REESE  LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA 


v 


PRACTICE   AND   THEORY 


OF  THE 


INJECTOR. 


BY 


STRICKLAND   I,.    KNEASS,   C.E., 

MEMBER  OF  THE  AMERICAN  SOCIETY  OF  MECHANICAL  ENGINEERS,  FRANKLIN 
INSTITUTE,  ENGINEERS'  CLUB  OF  PHILADELPHIA. 


REVISED   AND    ENLARGED. 


NEW    YORK: 

JOHN   WILEY   &   SONS. 

LONDON:   CHAPMAN  &  HALL,   LIMITED. 

1898. 


COPYRIGHT,    ±898, 

BY 
STRICKLAND   L.    KNEASS. 


PREFACE. 


Although  much  has  been  written  concerning  the 
theory  and  the  action  of  the  Injector,  there  have  been 
few  books  published  since  the  appearance  of  Giffard's 
own  pamphlet  in  1860,  which  have  been  based  directly 
upon  experimental  research. 

It  has  been  the  object  in  the  following  pages  to 
present  solutions  of  some  of  the  more  interesting 
problems,  with  illustrations  drawn  from  practical  tests? 
and  to  describe  in  detail  the  function  of  the  different 
parts.  To  the  professional  engineer  and  to  the  student, 
theoretical  discussion  of  the  Injector  is  a  tempting 
field,  because  of  the  beauty  of  its  underlying  princi- 
ple and  by  reason  of  the  numerous  associated  problems 
of  fluid  motion  ;  the  analysis  of  this  part  of  the  sub- 
ject, based  upon  carefully  conducted  laboratory  tests, 
has  been  fully  treated,  and  complex  formulae  have 
been  avoided  in  the  mathematical  discussion. 


111 


CONTENTS. 


CHAPTER    I.  PAGK 

EARLY  HISTORY i 

CHAPTER  II. 
DEVELOPMENT  OF  THE  PRINCIPLE .  .   .   ,      .   .     8 

CHAPTER   III. 

DEFINITION    OF    TERMS — DESCRIPTION    OF   THE    IMPORTANT 
PARTS  OF  THE  INJECTOR 25 

CHAPTER  IV. 
THE  DELIVERY  TUBE 30 

CHAPTER  V. 
THE  COMBINING  TUBE 44 

CHAPTER  VI. 
THE  STEAM  NOZZLE • 53 

CHAPTER  VII. 
THE  ACTION  OF  THE  INJECTOR c   . 67 

CHAPTER  VIII. 

APPLICATION    OF    THE    INJECTOR — AMERICAN    AND    FOREIGN 
PRACTICE 89 

CHAPTER  IX. 
DETERMINATION  OF  SIZE— TESTS 125 

CHAPTER  X. 

REQUIREMENTS  OF  MODERN  RAILROAD  PRACTICE — REPAIRS — 
METHODS  OF  FEEDING  L/OCOMOTIVE  BOILER 149 

INDEX 159 

iv 


THE  GIFFARD  INJECTOR. 


CHAPTER  I. 

EARLY   HISTORY. 

To  HENRI  JACQUES  GIFFARD,  an  eminent  French  mathe- 
matician and  engineer,  belongs  the  honor  of  having  invented 
the  simplest  apparatus  for  feeding  boilers  that  has  ever  been 
devised,  utilizing  in  a  novel  and  ingenious  way  the  latent 
power  of  a  discharging  jet  of  steam. 

From  the  time  of  his  graduation  from  LS  Ecole  Centrale 
in  1849,  Giffard  had  directed  his  energies  to  the  study  of 
aeronautics  and  had  spent  much  time  in  developing  a  light 
steam  motor  for  propelling  balloons;  it  is,  therefore,  not 
strange  that  he  should  also  have  attempted  to  devise  a  com- 
pact and  convenient  substitute  for  the  steam  pumps  then  in 
use.  Already  a  number  of  patents  had  been  granted  him  for 
the  application  of  the  steam  engine  to  aerial  navigation  and 
for  other  correlated  inventions  when,  on  May  8,  1858, 
letters  patent  were  issued  for  L'  Injecteur  Automoteur.  His 
early  technical  education  and  wonderful  ingenuity  well  fitted 
him  for  breaking  away  from  the  old  beaten  paths  and  start- 
ing out  on  a  new  line  of  discovery ;  and  in  view  of  the 
originality  of  his  work  he  fully  deserved  the  unqualified 
praise  accorded  him  by  his  contemporaries. 

Upon  purely  theoretical  grounds  the  method  by  which  he 
proposed  to  force  a  continuous  stream  of  water  into  the 
boiler  appeared  to  be  entirely  feasible  and  would,  if  practi- 
cable, possess  many  advantages  over  the  intermittent  sys- 
tems. The  difficulty  seemed  to  lie  in  fulfilling  the  peculiar 

i 


2  THE  GIFFARD  INJECTOR. 

conditions  required  for  the  condensation  of  the  steam  and 
the  subsequent  reduction  of  the  velocity  of  the  moving  mass. 
GifTard  carefully  considered  the  various  phases  of  the  ques- 
tion and  made  a  working  drawing  embodying  his  ideas.  A 
model  was  made  by  M.  Flaud  &  Cie.,  of  Paris,  who  found, 
however,  considerable  difficulty  in  forming  the  tubes  in  the 
peculiar  shapes  required.  But  in  the  shape  and  proportions 
of  the  nozzles  lay  the  element  of  success,  and  the  first  in- 
strument constructed  entirely  fulfilled  the  expectation  of  the 
designer. 

There  have  been  few  other  inventions  in  which  the  under- 
lying principles  have  been  so  thoroughly  worked  out  by  the 
original  inventor.  Giffard  seems  to  have  made  a  very  com- 
plete survey  of  the  possibilities  of  the  Injector  prior  to  placing 
it  before  the  public,  and  in  his  patent  specification,  describes  a 
number  of  improvements  that  have  since  been  made.  In  1860 
he  published  a  small  brochure  entitled  "  A  Theoretical  and 
Practical  Paper  on  the  Self-acting  Injector,"  in  which  he 
says :  "Of  all  the  necessary  accessories  of  a  Steam  Engine, 
perhaps  the  most  important  is  the  one  used  for  feeding  water 
to  the  boiler ;  upon  its  proper  working  depends  not  only  the 
regular  running  of  the  engine,  but  the  safety,  the  very  exis- 
tence of  those  who  approach  the  boiler  ;  .  .  .  .  nevertheless, 
by  a  kind  of  fatality,  the  apparatus  employed  up  to  the  pre- 
sent time  for  feeding  is,  of  all  others,  that  which  leaves  most 
to  be  desired."  After  reviewing  the  disadvantages  of  the 
various  methods  in  use,  he  continues,  "It  is  important, 
therefore,  to,create  a  new  method,  free  from  the  imperfection 
and  inconvenience  pointed  out,"  and  modestly  adds,  "  Such 
is,  it  appears  to  me,  the  result  obtained  by  the  apparatus  to 
which  I  have  given  the  name  of  Injector,  because  it  produces 
a  veritable  continuous  injection.  Its  mode  of  action,  extra- 
ordinary in  appearance,  contrary  to  that  which  wre  are  in  the 
habit  of  seeing  or  supposing,  is  explained  by  the  simplest 
laws  of  mechanics  and  has  been  foreseen  and  calculated  in 
advance."  He  describes  his  invention  in  detail  and  ex- 
plains very  fully  the  best  proportions  for  its  various  parts, 
and  also  the  mechanical  theory,  substantially  as  advanced 


EARL  Y  HISTOR  V.  3 

by  him  in  1850,  eight  years  before  the  construction  of  his  ex- 
perimental Injector. 

And  yet,  in  common  with  all  new  inventions  and  radical 
improvements,  great  difficulty  was  at  first  experienced  in  ob- 
taining a  fair  trial  of  its  merits,  and  in  many  cases  the  ex- 
aggerated claims  of  its  friends  interfered  as  much  with  its 
early  adoption  as  the  openly  expressed  criticism  of  its 
enemies.  The  great  advantages  of  the  new  method  were 
appreciated,  however,  by  the  Academic  des  Sciences  of 
France,  who  awarded  Giffard  the  Grand  Mechanical  Prize 
for  1859.  This  was  all  the  more  complimentary  as  it  was 
entirely  unsolicited.  Prominent  engineers  presented  before 
the  principal  scientific  societies  analytical  demonstrations  of 
the  theoiy  of  the  injector  and  allayed  to  a  great  extent  the 
suspicion  in  the  popular  mind  that  the  inventor  was  en- 
croaching dangerously  near  the  claim  for  perpetual  motion. 
Combes,  Bougere,  Reech,  Villiers,  Zuber  and  Pochet  are 
among  the  most  prominent  scientists  who  made  a  special 
study  of  the  subject,  and  the  demonstration  of  Pochet  is 
still  frequently  used  in  modern  text  books. 

It  must  not  be  supposed  that  Giffard  was  alone  in  his 
efforts  to  utilize  the  power  of  a  discharging  jet.  For  ex- 
hausting and  pumping  purposes  we  have  record  that  a  crude 
ejecting  apparatus  had  been  used  as  early  as  1570  by  Vitrio 
and  Philebert  de  Lorme.  But  the  first  device  that  bears  any 
similarity  to  the  principle  of  the  Injector  was  patented 
August  15,  1818,  by  Mannoury  de  Dectot,  who  describes 
"sundry  motors  or  means  for  employing  the  power  of  fire, 
of  steam,  of  air,  etc.,  to  start  the  movement  of  machines." 
He  applied  his  invention  for  raising  water  and  for  propelling 
boats  by  utilizing  the  expansion  and  condensation  of  steam 
in  connection  with  jets  of  water. 

Ravard  followed  in  1840  with  improved  forms,  but  the 
greatest  advance  was  made  by  Bourdon,  the  celebrated  in- 
ventor of  the  metallic  steam  gauge,  who  approached  very 
near  the  results  obtained  by  Giffard.  Two  patents  were 
issued  to  Bourdon,  one  in  1848  and  one  in  1857,  but  it  is  to 
the  latter  that  special  reference  will  be  made.  This  con- 


4  THE   GIFFARD  INJECTOR. 

tained  numerous  combinations  of  convergent  and  divergent 
tubes  for  transforming  the  energy  of  a  moving  jet,  or  for  dis- 
charging large  or  small  quantities  of  liquids  or  gases.  The 
similarity  of  the  form  of  the  apparatus  to  that  of  Giffard 
was  so  marked  that  the  question  of  priority  at  once  arose 
and  was  exhaustively  discussed  by  the  "  Societe  des  Inge- 
nieur  Civils"  It  was  shown  that  Giffard  was  wholly  un- 
aware of  the  last  improvement  of  Bourdon  when  he  applied 
for  his  patent,  and  as  he  had  publicly  presented  the  theory  of 
his  invention  nearly  seven  years  in  advance  of  Bourdon,  full 
credit  was  given  him  for  the  conception  of  the  Injector  and 
originality  in  the  application  of  the  principle. 

The  introduction  of  the  injector  into  England  by  Sharp, 
Stewart  &  Co.,  of  Manchester,  is  thus  described  by  one 
thoroughly  familiar  with  its  history  and  to  whom  its  early 
success  in  that  country  was  in  great  measure  due : 

"In  the  autumn  of  1859  when  our  representative  in  Paris 
sent  over  to  me  a  No.  4  Injector  as  a  curiosity  and  engineer- 
ing anomaly,  he  told  me  simply  what  it  did,  but  gave  no 
instructions  for  fixing  or  working.  At  about  the  same  time 
the  Paris  representative  of  Messrs.  Robert  Stephenson  &  Co., 
Newcastle,  sent  over  to  them  a  similar  Injector.  I  set  to 
work  at  once,  and  by  good  luck  coupled  up  the  correct  pipes 
to  their  proper  flanges,  but  was  a  great  deal  bothered  what 
to  do  with  the  overflow  flange.  After  a  few  nights'  work  I 
got  my  Injector  fixed  and  got  up  steam,  and  to  some  extent 
began  clumsily  experimenting  as  the  pressure  rose  to  60 
pounds,  the  full  working  pressure  of  the  boiler.  I  had  the 
Injector  fixed  over  a  tank  fed  by  a  ball  tap  and  closed  by  the 
boiler.  I  turned  steam  on  and  was  staggered  by  the  rush  of 
water  into  the  tank  from  the  overflow  pipe,  and  thought 
something  was  wrong.  However,  I  continued  to  turn  the 
steam  spindle,  and  the  escape  from  the  overflow  sensibly 
diminished  until  I  could  turn  no  further.  In  the  mean 
time  the  ball  tap  started  running  furiously  into  the  tank, 
showing  me  that  water  was  going  somewhere  and  I  knew  it 
could  go  nowhere  else  but  into  the  boiler.  I  then  began  to 
operate  with  the  four  thread  screw  at  the  side,  and  found 


EARLY  HISTORY.  5 

that  it  adjusted  the  water  supply,  and  succeeded  in  getting 
the  overflow  "dry."  I  then  opened  the  peep-holes  opposite 
the  space  between  the  combining  and  the  receiving  nozzles, 
and  saw  the  white  stream  passing  from  one  to  the  other  on 
its  way  to  the  boiler.  I  then  ceased  operations,  and  had  a 
pipe  of  tobacco,  and  let  some  water  out  of  the  blow-off  cock  ; 
then  I  tied  a  piece  of  spun  yarn  round  the  glass  water  gauge 
to  prepare  for  another  start,  and  shortly  after,  the  senior 
partner  came  round  for  a  stroll  and  found  me  operating.  I 
stopped  it,  started  it,  and  regulated  it  so  much  to  his  satis- 
faction that  within  one  week  the  monopoly  of  its  manufac- 
ture in  England  was  secured  by  the  firm.  Unfortunately  for 
Stephenson  &  Co.,  they  coupled  their  sample  Injector  up  in- 
correctly, and  it  would  not  work." 

For  stationary  service  the  Injector  did  not  at  first  become 
popular ;  possibly  on  account  of  the  mystery  that  seemed  to 
surround  its  working,  and  the  general  skepticism  as  to  its 
practical  wearing  powers.  Some  of  the  contributions  and 
queries  published  in  the  engineering  papers  of  the  day,  are 
very  amusing,  and  a  certain  writer  in  one  of  the  most 
prominent  weeklies  proves  most  conclusively  to  his  own 
and  probably  to  some  of  his  readers'  satisfaction,  that  the 
new  method  of  feeding  boilers  was  an  absolute  impossibility. 
The  injector  was,  however,  adopted  in  many  places  and 
continued  to  give  satisfaction.  In  the  first  trip  of  the 
"Great  Eastern"  Injectors  were  used  in  place  of  pumps, 
but  for  some  reason  not  explained,  they  were  subsequently 
removed  ;  this  may  have  been  owing  to  the  temperature  of 
the  feed  water  being  too  warm  for  efficient  service,  as  this 
was  the  weak  point  of  the  first  injectors  constructed. 

The  first  injector  applied  to  a  locomotive  in  England  was 
by  Mr.  J.  Cross,  Superintendent  of  the  St.  Helens  Railway. 
It  was  successful  from  the  start,  although  not  large  enough 
for  the  purpose  and  therefore  a  No.  8  was  substituted,  which 
proved  to  be  entirely  satisfactory. 

The  English  railroads  opened  a  wide  field  for  the  Injector; 
upon  most  of  the  locomotives,  the  earliest  feeding  pumps 
were  worked  by  hand,  but  afterwards  coupled  to  a  special 


6  THE  GIFFARD  INJECTOR. 

eccentric  or  to  the  crosshead.  Stretton,  in  his  recent  work 
on  the  Locomotive,  says  that  it  was  a  common  occurrence  for 
engines  with  a  single  pair  of  driving  wheels,  to  stand  on 
well  greased  rails  with  tender  brakes  fast  locked  and  drivers 
revolving,  in  order  to  fill  the  boiler  full  of  water.  But  even 
though  the  old  methods  were  very  crude,  engineers  in  Eng- 
land were  much  prejudiced  against  any  change,  even  for  the 
better.  By  way  of  illustration  the  following  incident  may 
be  given  of  a  successful  attempt  to  convince  an  obstinate 
engineer  against  his  will  ofk  the  advantages  of  the  injector  : 
"  Permission  had  been  obtained  from  the  Locomotive  Super- 
intendent of  one  of  the  principal  Railway  Companies  in 
Great  Britain  to  try  one  on  a  goods  engine,  and  for  me  to 
accompany  it  on  its  trial  trip,  with  a  loaded  goods  train, 
about  70  miles  out  and  70  miles  back.  On  the  outward 
journey  I  was  only  permitted  by  the  driver  to  make  short 
intermittent  trials  of  the  Injector,  he  depending  for  his  water 
supply  upon  his  pumps.  When  we  got  to  the  end  of  our 
outward  journey,  and  while  driver  and  firemen  were  having 
their  mid-day  meal  at  a  local  public  house,  I  went  to  the 
running  shed,  filled  up  the  boiler  with  the  injector  and  took 
out  the  balls  from  the  two  suction  clacks  and  put  them  in 
my  pocket.  We  had  not  gone  many  miles  on  our  return 
journey  when  water  was  wranted  in  the  boiler,  but  upon  the 
pumps  being  tried,  first  on  one  side,  then  on  the  other,  and 
naturally  refusing  to  work  without  suction  check  clacks,  I 
was  appealed  to,  to  put  my  Injector  on,  with  the  result  that 
we  completed  our  journey  without  delay  or  hitch  of  any 
kind,  depending  solely  on  the  one  No.  8  Injector.  The 
driver  consequently  reported  '  Pumps  out  of  order  and  could 
not  have  got  along  without  that  Injector.'  This  was  a 
grand  testimonial,  but  I  got  into  a  jolly  row  for  my  temeiity 
in  removing  the  clack  balls." 

The  Injector  was  introduced  in  the  United  States  by  Wm. 
Sellers  &  Co.,  who  commenced  its  manufacture  in  1860  at 
their  works  in  Philadelphia.  Of  locomotive  builders, 
Matthias  Baldwin,  was  the  first  to  use  the  new  instrument, 
applying,  in  September  1860,  a  No.  8  Injector  to  an  engine 


EARL  Y  HISTOR  Y.  7 

designed  for  the  Clarksville  and  Louisville  R.  R.  The  fol- 
lowing month  the  Detroit  and  Milwaukee  R.  R.  put  the 
Injector  in  use  on  one  of  their  locomotives,  and  the  Penn- 
sylvania and  the  Philadelphia  and  Reading  followed  in  the 
latter  part  of  the  same  year. 

To  Jos.  R.  Anderson  &  Co.,  Richmond,  Va.,  a  No.  4 
Injector  bearing  progressive  number  i,  was  shipped  in  Octo- 
ber 1860.  As  indicative  of  the  wearing  qualities  of  these 
early  instruments  Messrs.  Wm.  Sellers  &  Co.  state  that 
there  was  returned  to  them,  in  1887,  a  No.  4  Injector,  pro- 
gressive No-  7,  after  a  nearly  continuous  service  of  27  years, 
and  having  required  but  few  repairs  ;  it  further  is  interesting 
to  note,  that,  owing  to  improvements  recently  introduced, 
American  Injectors  are  now  extensively  used  in  France, 
and  have  been  adopted  as  a  standard  type  by  several  of  the 
government  railroads  in  the  country  of  its  inventor. 

It  need  hardly  be  said  that  the  Injector  is  the  most  popular 
boiler  feeder  now  in  use.  There  have  been  more  than  500,- 
ooo  manufactured  in  this  country  for  the  various  kinds  of 
service,  and  there  is  scarcely  a  locomotive  in  the  world  that 
is  not  equipped  with  one  or  two  Injectors.  Compact,  reliable 
and  economical,  it  still  deserves  the  high  encomium  bestowed 
upon  it  in  1859,  by  M.  Ch.  Combes,  Inspector  General  and 
Director  L^  Ecole  des  Mines, — "  It  is  without  doubt  better 
than  all  devices  hitherto  used  for  feeding  boilers,  and  the 
best  that  can  be  employed,  as  it  is  the  simplest  and  most  in- 
genious." 


CHAPTER  II. 

DEVELOPMENT  OF  THE   PRINCIPLE. 

GIFFARD  having  established  beyond  doubt  the  power,  of  a 
discharging  jet  of  steam  to  lift  a  mass  of  feed  water  many 
times  its  own  weight  and  force  it  against  the  initial  pressure, 
it  became  necessary  to  prepare  the  constructive  details  of  the 
new  boiler  feeder.  The  arrangement  decided  upon,  could  not 
in  the  light  of  subsequent  events  be  considered  as  an  entire 
success,  as  it  contained  inherent  defects  that  caused  frequent 
failures  and  prevented  the  placing  of  as  much  confidence  in 
the  new  boiler  feeder,  as  the  merits  of  the  invention  deserved. 
Many  locomotives  that  at  first  were  equipped  with  two  in- 
jectors, were  afterward  altered  so  as  to  have  a  pump  upon  the 
left  hand  side  to  be  used  in  case  the  injector  should  refuse  to 
work,  and  it  was  not  until  1875  or  1876  that  more  recent 
improvement  in  construction  restored  the  confidence  that 
the  original  defects  had  forfeited,  and  the  pump  was  driven 
from  service  upon  locomotives  in  the  United  States ;  even 
yet  upon  some  of  the  Knglish  Railways,  a  pump  is  used  on 
one  side  of  the  engine,  arranged  somewhat  in  the  manner  of 
the  pressure  or  vacuum  pump  for  the  air  brakes. 

The  curves  of  the  tubes  and  nozzles  as  laid  down  by 
GiiFard  were  beyond  criticism,  and  are  still  used  when  this 
type  of  injector  is  manufactured  ;  his  thorough  knowledge 
of  the  laws  governing  the  action  of  the  jet  and  the  accelera- 
ting velocity  of  the  moving  mass,  enabled  him  so  to  con- 
struct the  curves  of  approach  and  recession,  that  they  have 
been  used  as  a  prototype  for  all  subsequent  forms  of  injec- 
tors ;  except  for  one  change  advanced  by  our  increased  in- 
formation regarding  the  action  of  steam  during  expansion, 
and  a  few  minor  modifications  for  economy  of  manufacture, 
8 


DEVELOPMENT  OF  THE  PRINCIPLE.  9 

or  for  adapting  the  injector  to  special  purposes,  no  change 
in  the  contour  of  the  tubes  has  been  made. 

But  that  there  has  been  development,  cannot  be  denied  ; 
it  may  be  considered  as  following  three  lines : 

First.  Constructive  changes. 

Second.  Carrying  out  the  ideas  suggested  by  Giffard  in 
his  pamphlets  or  patent  specifications. 

Third.  The  discoveries  of  new  properties  of  the  jet,  or 
the  application  of  new  principles. 

Almost  all  important  inventions  follow  in  this  natural 
sequence  during  their  development,  and  the  injector  was  no 
exception  to  the  rule.  Genuine  mechanical  ability  is  seldom 
combined  with  inventive  genius,  and  it  almost  always  follows 
that  the  fullest  development  is  obtained  in  other  hands  than 
those  of  the  original  inventor.  The  first  improvements  were 
therefore  in  the  line  of  correcting  the  defects  that  became 
apparent  after  the  injector  had  been  subjected  to  the  test  of 
actual  service  ;  changes  required  to  facilitate  repairs,  or  the 
adjustment  of  the  positions  of  the  tubes.  In  the  second  di- 
vision lies'  the  basis  of  many  subsequent  improvements  that 
have  since  proved  valuable,  and  Giffard  has  never  been 
given  sufficient  credit  for  his  wonderfully  wide  grasp  of  the 
possibilities  or  future  development  of  the  injector.  Of  the 
third  there  will  be  less  to  relate,  as  the  only  real  advance 
has  been  with  the  discovery  of  the  peculiar  property  of  the 
movjng  jet  by  which  the  instrument  was  made  self-regu- 
lating, and  with  the  novel  arrangement  of  tubes  by  which 
the  re-starting  feature  was  added. 

The  general  appearance  of  the  injector  as  now  constructed 
is  entirely  different  from  the  original  form,  and  it  would  be 
difficult  for  any  one  not  specially  familiar  with  the  subject 
to  recognize  one  made  in  1858 ;  the  arrangement  of  the  ad- 
justing handles,  peculiarly  shaped  body,  and  queer  little  peep 
holes  present  to  the  modern  eye  a  very  odd  appearance,  while 
the  heavy  flanged  pipe  connections  and  steam  cock  do  not 
contrast  at  all  favorably  with  the  neater  form  now  used  on 
American  boilers. 

Figure  i  shows  a  sectional  view  of  the  earliest  form  of  in- 


THE  GIFFARD  INJECTOR. 

<o 


DEVELOPMENT  OF  THE  PRINCIPLE.  11 

jector  manufactured  for  public  sale,  and  was  intended  for 
use  on  either  stationary  or  locomotive  boilers ;  it  was  made 
entirely  of  brass,  with  the  body  composed  of  three  pieces, 
screwed  and  bolted  together,  and  the  steam,  feed,  and  boiler 
connections  terminating  in  flanges,  as  is  still  the  general 
practice  in  England  and  on  the  continent.  The  method  of 
starting  and  operating  the  injector  was  as  follows  :  upon 
opening  the  cock  A ,  steam  from  the  boiler  passed  freely  into 
the  steam  ram  a'  through  the  small  drilled  holes  a" ;  the  spin- 
dle, which  had  been  previously  forced  down  to  a  tight  bearing 
against  the  taper  steam  nozzle  a,  was  drawn  back  one  turn 
of  the  handle  F,  exposing  an  annular  area  approximately 
one-quarter  that  of  the  end  of  the  tube  b.  The  rapid  dis- 
charge of  the  steam  through  the  combining  tube  b,  entrained 
the  air  in  the  suction  branch  B,  and  formed  a  partial  vacuum 
in  the  feed  pipe  which  raised  the  water  to  the  injector;  the 
spindle  was  then  drawn  fully  back,  and  the  increased  dis- 
charge of  steam  imparted  to  the  surrounding  body  of  water, 
during  its  passage  through  the  combining  tube,  sufficient 
velocity  to  cross  the  overflow  space  d,  and  enter  the  boiler 
through  the  delivery  tube  c. 

Assuming  the  correct  relation  to  exist  between  the  dis- 
charge area  of  the  steam  nozzle  and  the  annular  entrance 
area  for  the  water  at  the  larger  end  of  the  combining  tube, 
the  steam  will  force  into  the  boiler  many  times  its  weight  of 
water,  without  tendency  to  spill  at  the  overflow  d ;  if  change 
take  place  in  the  pressure  of  the  steam  or  of  the  feed  water, 
one  of  two  conditions  will  be  introduced,  depending  upon 
the  direction  in  which  the  changes  of  pressure  occur :  either 
there  will  be  an  insufficient  supply  of  water  for  perfect  con- 
densation during  the  passage  of  the  jet  through  the  combin- 
ing tube,  or  too  great  a  quantity  of  water  will  enter  the  in- 
jector to  pass  through  the  delivery  tube  c.  It  was  to  allow 
for  this,  that  Giffard  introduced  two  adjustments:  one  for 
the  water  area  by  giving  an  axial  movement  to  the  ram  and 
steam  nozzle  by  the  lever  G,  and  the  other  for  the  steam  dis- 
charge area  by  the  handle  F  on  the  spindle  ;  if  the  pressure 
of  the  steam  or  the  lift  of  feed  water  were  increased,  it  was 


12  THE  GIFFARD  INJECTOR. 

necessary  to  draw  the  steam  ram  further  back  to  permit  the 
admission  of  a  larger  quantity  of  water,  while  a  fall  of  pres- 
sure would  require  a  reverse  movement.  This  necessity  for 
re-adjustment  was  so  frequent  upon  locomotives  where  the 
pressure  was  subject  to  wide  fluctuation,  that  the  packing 
upon  the  steam  ram  soon  wore  loose  and  gave  constant 
trouble,  allowing  leakage  to  occur  between  the  steam  and 
feed  chambers,  impairing  seriously  the  efficiency  of  the  in- 
jector and  its  power  of  suction.  This  packing  was  formed 
in  an  ingenious  manner,  although  in  service  it  was  found  in- 
effective, and  no  device  has  yet  been  introduced  that  has 
proved  thoroughly  reliable  for  this  purpose.  The  ram  was 
provided  with  three  kinds  of  packing :  the  lower  part  was  first 
turned  slightly  larger  than  the  bore  of  the  body,  and  small 
triangular  grooves  s  turned,  not  spirally,  but  in  planes  nor- 
mal to  the  axis ;  the  ram  was  then  driven  to  place,  forcing 
the  tops  of  the  sharp  edges  backward  and  reducing  it  to  the 
same  size  as  its  bearing.  A  deeper  groove  p'y  was  filled 
with  rubber  or  hemp,  and  a  second  groove  /,  with  a  split 
metallic  ring;  while  another  set  of  V's  was  placed  between 
the  ring  and  the  steam  nozzle.  Upon  the  body  of  the  in- 
jector and  directly  opposite  the  overflow  d,  four  peep  holes 
were  placed  and  covered  by  a  sliding  ring  with  handles  d'  ; 
this  could  be  rotated  until  the  holes  in  the  ring  were  oppo- 
site those  in  the  body,  and  permitted  the  inspection  of  the 
condition  of  the  passing  jet.  When  new  and  in  good  con- 
dition this  injector  worked  very  well  and  its  double  adjust- 
ments gave  it  long  wearing  power ;  any  ordinary  increase 
in  the  diameter  of  the  nozzle  due  to  the  attrition  of  the 
rapidly  moving  jet,  could  be  counteracted  by  a  change  in 
the  areas,  although  at  a  reduction  of  the  efficiency. 

As  the  constructive  defects  of  the  injector  were  obvious, 
the  first  changes  introduced  were  improvements  in  the 
packing  of  the  steam  ram,  and  those  manufactured  in  this 
country  in  1860  were  provided  with  a  conical  stuffing  box 
filled  with  a  number  of  split  rings  made  of  metal  softer  than 
the  body ;  but  unequal  wear  upon  the  ram  soon  caused  leak- 
age with  this  system  also.  It  is  singular  that  the  merits  of 


DEVELOPMENT  OF  THE  PRINCIPLE.  13 

the  fixed  nozzle  injector  were  not  earlier  appreciated.  Mill- 
holland,  of  Reading,  Pa.,  patented  in  1862,  an  injector 
formed  of  non- adjustable  tubes,  depending  upon  the  use  of 
external  valves  for  regulation ;  but  this  met  with  no  success, 
and  does  not  appear  to  have  ever  gained  publicity.  Internal 
adjustments  seem  to  have  been  regarded  as  all  important, 
for  the  early  Giffard  injectors  were  not  provided  with  check 
valves  upon  the  overflow,  and  any  reduction  of  the  water 
supply  would  cause  considerable  indraft  of  air  to  the  boiler 
unless  counteracted  by  corresponding  reduction  in  the  steam 
discharge ;  the  avoidance  of  the  check  valve  may  have  been 
intentional,  and  due  to  the  weak  form  of  lifting  jet  em- 
ployed, as  the  power  of  suction  was  affected  by  the  slightest 
increase  in  resistance  to  the  free  discharge  of  the  steam. 
Subsequently,  fixed  nozzle  injectors  came  into  extensive  use 
and  are  now  applied  to  many  kinds  of  service. 

As  the  problem  of  successfully  packing  the  steam  ram 
seemed  impossible  of  solution,  Robinson  &  Gresham  of 
Manchester,  England,  attempted  in  1864,  the  plan  of  regu- 
lating the  water  area  by  moving  the  combining  and  delivery 
tubes  toward  or  from  a  fixed  steam  nozzle  ;  a  pinion  meshing 
into  a  rack  cut  upon  the  exterior  of  the  tube  was  actuated 
by  a  hand  wheel  on  the  body,  and  a  long  cylindrical  bearing 
upon  the  outside  of  the  delivery  tube  prevented  any  serious 
leak  from  the  boiler  pipe.  A  similar  device  was  introduced 
in  1868,  by  Samuel  Rue  of  Philadelphia,  who  applied  stuff 
ing  boxes  to  the  ends  of  each  tube,  and  regulated  their 
position  by  means  of  a  hand-lever ;  the  fundamental  problem, 
was,  however,  to  make  the  adjustments  of  the  water  supply 
automatic,  and  eliminate  as  far  as  possible  the  necessity  for 
watchful  care  on  the  part  of  the  engineer.  GifFard  had 
already  described  in  his  patent  specification  two  methods  by 
which  this  could  be  obtained ;  one  by  placing  a  spring  be- 
hind a  movable  steam  nozzle  in  such  a  manner  that  an 
increase  of  pressure  would  cause  compression  of  the  spring, 
and  elongate  the  distance  between  the  tubes,  while  the  re- 
silience of  the  spring  would  regulate  properly  for  a  converse 
condition.  This  was  never  put  into  practical  operation,  and 


14  THE  GIFFARD  INJECTOR. 

it  is  easy  to  see  difficulties  that  would  discourage  the 
attempt.  The  other  suggestion  was  to  vary  the  pressure  of 
the  entering  water  by  subdividing  the  steam  jet  and  using 
the  first  or  subsidiary  apparatus,  for  feeding  the  second  or 
forcing  set  of  tubes  under  a  pressure  that  would  vary  in  pro- 
portion to  the  requirements.  A  still  simpler  method  was 
that  patented  by  Win.  Sellers  of  Philadelphia  in  August 
1865,  by  which  any  change  in  the  internal  condition  of  the 
jet  would  actuate  a  set  of  movable  tubes  so  that  the  correct 
proportion  of  the  water  to  the  steam  would  always  be  ob- 
tained. 

Ever  since  the  introduction  of  the  Injector,  the  advan- 
tage of  an  automatic  adjustment  was  realized,  and  a  series 
of  experiments  had  been  carried  on  by  \Vm.  Sellers  & 
Co. ,  for  the  purpose  of  attaining  this  end ;  after  numerous 
experimental  devices  had  been  thrown  aside  the  injector 
shown  in  section  in  Fig.  2,  was  tested  and  found  to  work 
satisfactorily.  The  basis  of  the  invention  was  the  discovery 
of  the  strong  vacuum  produced  by  the  moving  jet  in  a 
closed  overflow  chamber  when  the  water  supply  was  reduced 
below  the  maximum,  and  that  an  excess  of  feed  water  would 
cause  the  pressure  in  a  confined  overflow  chamber  to  rise 
above  that  of  the  atmosphere  before  the  jet  would  break.  Now 
as  the  most  efficient  performance  of  an  injector  is  when  the 
pressure  of  the  jet  while  crossing  the  overflow  is  the  same 
as  that  of  the  atmosphere, — indicating  that  the  density  is  ap- 
proximately unity  and  that  the  steam  entirely  condensed,— 
it  only  remained  to  compel  the  condition  of  the  overflow  to 
influence  the  water  entrance  to  the  combining  tube.  Any 
variation  of  the  steam  and  water  supply  would  then  first 
affect  the  absolute  pressure  in  the  overflow  chamber,  and 
this  would  immediately  respond  upon  the  water  admission 
by  a  proper  movement  of  the  combining  tube. 

Fig.  2  gives  a  sectional  view  of  one  of  the  earliest  experi- 
mental forms  of  this  device  with  constructive  details  inten- 
tionally omitted.  Steam,  feed,  and  boiler  connections  are 
indicated  by  the  letters  A,  B,  and  C,  and  the  steam  nozzle, 
combining  tube  and  delivery  tube,  by  a,  b,  and  c ;  D  is  a  closed 


DEVELOPMENT  OF  THE  PRINCIPLE. 


15 


overflow  chamber,  communicating  wilh  the  interior  of  the 
tubes  through  the  overflow  d,  situated  slightly  above  the 
minimum  diameter  of  the  bore  of  the  tube.  The  delivery 
tube  c  passes  completely  through  the  delivery  chamber  C, 
and  is  packed  by  stuffing  boxes  g  and  h  of  equal  diameter, 
and  is  therefore  balanced  with  reference  to  any  pressure 
carried  in  the  boiler,  so  that  the  tubes  are  free  to  move  under 
the  influence  of  any  pressure  within  the  chamber  D,  acting 
upon  the  differential  areas  of  the  piston  b'  and  outside  of  the 
delivery  tube  c.  As  discharge  from  the  overflow  chamber 
was  not  permitted,  the  injector  was  started  by  means  of  a 
valve  placed  in  the  boiler  branch  Cand  not  shown  in  the  illus- 
tration. Two  years  later  it  was  discovered  that  the  pressure 
in  D  was  strong  enough  to  obviate  the  use  of  the  balanced 


delivery  tube,  and  the  simpler  form  shown  in  Fig.  3  was  de- 
vised. It  could  be  placed  in  any  position,  horizontally  or 
vertically,  as  gravity  had  no  appreciable  effect  upon  its 
action.  -  Using  the  same  nomenclature  as  before,  a  is  the 
steam  nozzle,  b  the  combining  tube  and  c  the  delivery  tube ; 
the  operation  was  as  follows :  the  starting  valve  D,  placed 
below  the  delivery  tube  was  opened  and  free  discharge 
given  for  the  lifting  steam  jet  issuing  from  a  small  hole 
drilled  in  the  steam  spindle.  This  gave  a  strong  suction 
vastly  superior  to  the  lifting  power  of  the  original  Giffard 
injector,  and  being  in  excess  of  the  requirements  of  the  or- 
dinary height  of  lift,  produced  a  lower  pressure  in  the  closed 
chamber  d  than  in  the  feed  pipe.  The  combining  tube 
would  therefore  move  down  to  the  lower  end  of  its  stroke 
exposing  full  admission  area  for  the  water,  until  the  rising  of 


16 


GIFFARD  INJECTOR. 
FlG.  3. 


D 


DEVELOPMENT  OF  THE  PRINCIPLE.  17 

the  water  and  condensation  of  the  issuing  steam  jet  caused  a 
nearly  perfect  vacuum,  which  drew  the  tube  to  the  other  end 
of  its  stroke.  As  the  spindle  was  drawn  slowly  back,  the 
proportion  of  steam  became  too  great  for  immediate  conden- 
sation, and  the  contraction  of  the  jet  continued  while  crossing 
the  overflow ;  the  ensuing  vacuum  in  the  overflow  chamber, 
acting  upon  the  piston  head  of  the  combining  tube  drew  the 
tube  away  from  the  steam  nozzle,  admitting  an  increased 
supply  of  water.  It  follows  that  regulation  would  occur  with 
any  change  in  the  steam  supply,  whether  that  change  be 
produced  by  a  variation  of  the  pressure  of  the  boiler,  or  of 
the  effective  area  of  the  steam  nozzle.  When  the  spindle  is 
drawn  fully  back,  the  starting  valve  D  is  closed  and  the 
feeding  of  the  boiler  established.  It  follows,  therefore,  that 
a  reduction  in  capacity  of  the  injector  may  be  effected  by 
running  the  spindle  part  way  down  into  the  steam  nozzle, 
and  the  water  supply  will  be  automatically  reduced  in  pro- 
portion ;  at  any  fixed  steam  pressure  the  temperature  of  the 
water  delivered  to  the  boiler  will  be  nearly  the  same  for 
both  the  maximum  and  minimum  capacity ;  a  change  in  the 
height  of  lift  would  diminish  the  quantity  of  feed  water, 
until  a  downward  motion  of  the  combining  tube,  due  to  the 
increased  vacuum  in  the  closed  overflow  chamber,  would 
compensate  by  increased  area,  the  loss  of  velocity  due  to 
the  reduction  in  the  difference  of  pressure  between  the  in- 
terior of  the  combining  tube  and  the  height  of  lift.  This 
method  of  regulation  gives  exceedingly  good  results  over  a 
wide  range  of  pressure,  and  with  an  expenditure  of  steam 
that  is  proportional  to  the  work  performed. 

From  an  inspection  of  Fig.  3,  it  will  be  seen  that  the  per- 
formance of  the  injector  depends  upon  the  tightness  of  the 
joint  between  the  delivery  tube  b,  and  its  sleeve  bearing, 
just  as  the  original  form  relied  upon  the  packing  of  the  ad- 
justable steam  nozzle.  Unequal  wear  of  this  part  permitted 
leakage  between  the  boiler  and  the  overflow  chamber, 
although  not  as  rapidly  nor  to  so  fatal  an  extent  as  in  the 
former  case. 

This  led  to  the  application  of  the  discovery  previously 
2 


18  .       THE  GIFFARD  INJECTOR. 

made  by  Gresham,  that  the  overflow  space  between  the  com- 
bining and  delivery  tubes  could  be  lengthened  without 
materially  affecting  the  efficiency,  and  in  1873  this  form  of 
injector  was  still  further  improved  by  separating  the  com- 
bining tube  from  the  delivery  tube,  screwing  the  latter  into 
the  body,  and  permitting  the  combining  tube  free  movement 
toward  and  from  the  steam  nozzle ;  this  altered  the  length 
of  the  overflow  space  with  every  change  in  the  position  of  the 
tube;  with  low  pressure,  the  combining  tube  was  drawn 
close  to  the  steam  nozzle,  exposing  the  maximum  length  of 
overflow  space ;  as  the  pressure  rose,  this  distance  was  re- 
duced and  the  length  of  the  overflow  at  the  higher  pressure 
was  less  than  that  used  in  the  older  form  of  injector. 

The  principle  and  development  of  this  invention  has  been 
explained  in  detail  on  account  of  its  merit  and  originality. 
In  an  improved  and  modified  form  this  injector  is  exten- 
sively used  at  the  present  time,  and  still  preserves  the  pecu- 
liar principle  that  made  it  such  an  advance  over  the  earlier 
instruments  employed. 

The  other  method  of  automatically  regulating  the  water 
supply,  by  subdividing  the  actuating  steam  jet,  was  intro- 
duced in  the  United  States  in  1876-7,  when  two  American 
patents  were  issued;  one  to  Ernest  Korting  of  Hanover, 
Prussia,  and  the  other  to  John  Hancock  of  Boston  ;  foreign 
patents  had  already  been  granted  to  the  former,  who  had 
been  a  manufacturer  and  experimenter  for  many  years.  The 
devices  were  practically  alike  ;  the  invention  consisted  in 
combining  two  sets  of  tubes,  and  each  set  was  proportioned 
to  the  function  it  had  to  perform.  A  small  steam  nozzle 
discharged  into  a  large  combining  tube,  which  delivered  the 
feed  water  under  a  slight  pressure  to  the  entrance  of  the 
smaller  combining  tube  of  the  forcing  set,  where,  meeting 
the  steam  issuing  from  a  larger  nozzle,  the  water  received 
an  additional  impulse  sufficient  to  force  it  into  the  boiler ; 
the  increase  in  feeding  capacity  of  the  first  set  of  tubes  with 
a  rise  in  the  steam  pressure,  obviated  the  necessity  for  any 
regulation  of  the  water  supply  to  allow  for  fluctuation  in 
the  pressure  carried  in  the  boiler. 


DEVELOPMENT  OF  THE  PRINCIPLE. 


19 


A  section  of  this  injector  is  shown  in  Fig.  4  where  a  and  b 
are  the  tubes  of  the  second,  or  forcing  set,  a  and  b\  of  the 
lifting  set ;  an  overflow  cock  is  placed  beyond  each  delivery 
tube  for  the  purpose  of  starting,  as  no  overflow  aperture 
separates  the  convergent  combining  tube  from  the  divergent 
delivery  tube.  The  proportions  in  which  the  sets  differ  are 
apparent;  the  first  set  is  primarily,  an  ejector,  as  the 
diameter  of  the  steam  nozzle  is  less  than  that  of  its  delivery 
tube.  In  the  other  set  the  conditions  are  reversed,  and  an 
injector  is  formed  which  is  capable  of  forcing  the  feed  water 
against  a  pressure  considerably  above  that  of  the  initial  jet. 
A  separate  valve  is  provided  for  each  steam  nozzle,  so  that 


by  admitting  steam  first  to  af,  the  feed  water  is  raised  and 
flows  from  the  waste  cock  c? ;  this  is  now  closed,  compelling 
the  water  to  pass  through  the  smaller  combining  tube  b' , 
the  steam  nozzle  a  is  now  opened  and  the  jet  established 
through  the  forcing  combining  tube,  aided  by  the  velocity 
of  the  entering  water  due  to  the  pressure  produced  by  the 
delivery  tube  of  the  lifting  set ;  the  closing  of  the  final  waste 
cock  d  compels  the  water  to  enter  the  boiler. 

The  self-adjusting  principle  of  the  Double  Jet  Injector 
depends  upon  the  variation  of  feed  pressure  when  the  water 
entrance  to  the  combining  tube  is  constant.  Numerous 
changes  have  since  been  made  in  the  special  devices  by 
which  the  necessary  sequence  of  opening  and  closing  the 


20  THE  GIFFARD  INJECTOR. 

various  steam  and  waste  valves  could  be  obtained.  In  its 
modern  form,  this  injector  is  very  convenient  to  operate,  and 
the  principle  of  its  construction  is  incorporated  in  many  of 
the  best  known  injectors  of  the  present  day. 

In  tracing  the  development  of  the  self-adjusting  principle, 
several  other  improvements  of  the  more  elementary  forms 
have  necessarily  been  omitted ;  these  will  now  be  taken  up 
as  nearly  as  possible  in  the  order  of  their  introduction. 

In  this  country  the  self-adjusting  injector  was  so  early 
perfected,  and  it  so  largely  superseded  the  original  form,  that 
few  other  improvements  were  made  until  the  approach  of 
the  expiration  of  Giffard's  patents.  In  England  and  France, 
the  form  of  the  injector  as  manufactured  by  Sharp,  Stewart 
&  Co.,  and  H.  Flaud  &  Cie.,  was  modified  in  various  ways; 
Stewart,  Robinson  and  Gresham,  brought  out  several  meri- 
torious inventions.  Among  the  most  important  of  these 
were  the  adjustable  combining  tube,  which  has  already  been 
described,  and  the  separation  of  the  lifting  apparatus  from 
the  injector  proper;  in  the  latter  case  an  ejector,  whose  only 
function  was  to  raise  the  feed  water,  was  connected  with  the 
overflow  aperture  of  the  combining  tube,  and  by  its  aid  the 
injector  could  be  started  with  great  facility.  In  1863  the 
same  firm  patented  an  arrangement  by  which  the  injector 
was  placed  below  the  level  of  the  water  in  the  tank  of  a 
locomotive ;  the  waste  pipe  from  the  overflow  extended  up 
into  the  cab  above  the  water  level,  and  any  waste  from  the 
injector  could  be  readily  seen  and  corrected;  further,  the 
drip  pipe  was  connected  with  the  suction,  and  loss  of  feed 
water  from  any  cause  prevented. 

In  France,  the  few  improvements  that  were  added,  were 
chiefly  in  the  line  of  English  models.  Turck  followed 
Gresham  in  the  use  of  a  stationary  steam  nozzle,  and  in  ad- 
dition applied  an  enveloping  nozzle,  enclosing  an  air  space, 
in  order  to  prevent  transmission  of  heat  from  the  steam  to 
the  surrounding  feed  water.  Cuau  brought  out  an  injector 
in  which  all  the  tubes  were  fixed,  and  so  proportioned  as  to 
permit  the  use  of  water  ot  very  high  temperature ;  no  lifting 
spindle  was  provided,  but  the  feed  water  was  raised  by 


DEVELOPMENT  OF  THE  PRINCIPLE.  21 

an  auxiliary  ejector.  Bouvret,  Polonceau,  and  Delpeche, 
followed  with  comparatively  unimportant  modifications, 
although  all  have  lent  their  name  to  styles  used  upon  rail- 
roads in  France. 

As  no  patent  was  allowed  Giffard  in  Austria  and  Ger- 
many, his  injector  was  manufactured  by  unlicensed  parties 
soon  after  its  introduction  in  France,  and  much  original  in- 
vestigation was  started.  Schau  discovered  the  advantage 
of  the  divergent  steam  nozzle  in  1869,  by  which  the  expan- 
sion of  the  steam  is  utilized  to  better  advantage  than  with 
the  convergent  shape.  Haswell,  Korting,  Pradel,  and 
Krauss,  introduced  special  changes,  many  of  which  are  still 
in  service.  Korting,  whose  invention  of  the  double  jet  in- 
jector has  already  had  special  consideration,  was  granted  a 
patent  in  1872  for  drawing  exhaust  steam  from  the  cylinder 
into  the  injector,  by  which  the  temperature  of  the  water 
delivered  to  the  boiler  was  considerably  raised ;  an  opening 
was  made  in  the  combining  tube  at  a  point  where  a  strong 
suction  was  produced  by  the  condensation  of  the  motive  jet : 
the  inventor  states  in  his  specifications  that  the  injector 
could  be  used  with  live  steam  alone,  and  that  the  supple- 
mentary overflow  enabled  it  to  start  very  easily.  Friedman 
in  1879,  patented  an  improved  fixed  nozzle  injector,  and  in 
the  form  in  which  he  placed  it  upon  the  market,  used  a  sup- 
plementary opening  in  the  combining  tube  for  the  entrance 
of  an  additional  supply  of  feed  water ;  this  system  possessed 
a  number  of  advantages,  and  after  undergoing  subsequent 
modification  is  now  extensively  used  both  in  Germany  and 
the  United  States. 

In  England  in  1877,  Hamer,  Metcalf  &  Davies,  obtained 
a  patent  for  an  injector  in  which  there  was  a  very  large 
steam  nozzle,  and  a  combining  tube  with  a  hinged  section 
extending  nearly  its  full  length ;  these  modifications  were 
made  for  the  purpose  of  using  exhaust  steam  for  the  actua- 
ting jet,  and  the  injector  was  enabled  to  feed  boilers  carrying 
as  high  as  80  Ibs.  pressure ;  the  tubes  were  well  designed 
and  showed  much  ingenuity  in  their  construction. 

Returning  to  American  improvements  we  find  Garner  C- 


22 


THE   GIFFARD   INJECTOR. 


Williams  of  -  Ellenville,  N.  Y.,  made  in  1880  application  for 
a  patent  for  the  first  self-starting  injector ;  *  it  was  very  ingen- 
iously constructed,  but  seems  never  to  have  appeared  upon 
the  market.  John  Loftus,  of  Albany,  N.  Y.,  followed  in 
r88i  with  a  simpler  device,  shown  in  Fig.  5,  which  differed 
from  all  previous  forms  by  the  insertion  of  a  cylindrical  suc- 
tion or  draft  tube  b' ',  between  the  steam  nozzle  and  the  com- 
bining tube.  This  obviated  the  necessity  for  a  special 
priming  device,  as  th£  opening  of  an  ordinary  globe  valve 
in  the  steam  pipe  would  produce  a  vacuum  in  the  water 
branch  sufficient  for  all  ordinary  lifts.  Check  valves  h  ti 
were  placed  on  the  separate  overflow  chambers  D,  D' ,  so 
that  the  condition  of  the  jet  while  crossing  the  starting 


overflow  d,  was  independent  of,  and  uninfluenced  by,  its  con- 
dition at  the  upper  or  supplemental  overflow  d'.  Bancroft, 
Gresham,  Penberthy,  Desmond,  Derby  and  others,  altered 
and  improved  the  arrangement  of  the  valves  and  tubes  of  the 
re-starting  injector  and  increased  the  efficiency  of  its  per- 
formance. 

In  1885,  J.  Sellers  Bancroft  of  the  firm  of  Wm.  Sellers  & 
Co.,  of  Philadelphia,  patented  a  modification  of  the  double 
jet  principle,  in  which  the  re-starting  feature  was  introduced  ; 
starting  and  supplementary  overflows  were  so  placed  in 
the  combining  tubes  of  the  forcing  and  the  lifting  sets, 
that  free  discharge  from  the  steam  nozzles  was  obtained, 
producing  a  strong  vacuum  in  the  suction  pipe.  This  form 

*  Subsequent  research  shows  that  a  re-starting  injector  was  patented  in  France  by 
Vabe,  Nov.  12,  1878. 


DEVELOPMENT  OF  THE  PRINCIPLE.  23 

of  injector  was  not  placed  upon  the  market,  as  further  ex- 
periment by  the  same  firm  developed  the  arrangement  shown 
in  Fig.  6,  invented  by  the  author  in  1887.  This  injector 
consists  of  a  double  set  of  tubes  arranged  in  axial  line, 
giving  continuous  acceleration  to  the  jet  from  the  moment 
the  water  enters  the  draft  tube.  A,  B,  C,  are  the  steam, 
feed,  and  boiler  connections;  a',  an  annular  lifting  steam 
nozzle  discharging  through  the  annular  draft  tube  b ',  and  a 
the  forcing  steam  nozzle  from  which  the  jet  receives  the  final 
impulse  sufficient  to  enter  the  boiler.  The  overflow  open- 
ings d,  d' ',  d" ,  are  all  contained  in  a  chamber  Z>,  communi- 
cating with  the  large  waste  pipe  D'  only  by  the  opening  of 
the  waste  valve  h  :  these  overflow  apertures  are  of  such  pro- 
portion and  so  distributed  that  free  discharge  is  obtained  for 


the  lifting  steam  nozzle  a'.  The  resultant  vacuum  in  the 
feed  pipe  always  tend  to  raise  the  water  to  the  injector  after 
a  temporary  interruption  of  the  water  supply  and  restore 
the  continuity  of  the  jet,  while  the  arrangement  of  the  tubes 
and  steam  nozzles  permit  wide  variation  of  steam  pressures 
without  waste  at  the  overflow. 

In  1890  another  form  of  locomotive  injector  was  invented 
by  Holden  and  Brooks,  of  Salford,  England,  who  had 
already  secured  several  patents  for  fixed  nozzle  exhaust 
steam  injectors ;  this  device  combined  the  use  of  exhaust 
and  live  steam,  with  the  tubes  arranged  as  in  the  double  jet, 
and  so  contrived  for  automatic  action,  that  opening  valves 
in  the  feed  and  exhaust  pipe  would  start  the  injector  even 
against  the  high  pressures  carried  in  locomotive  boilers. 


24  THE  GIFFARD  INJECTOR. 

There  have  been  numerous  other  changes  made  upon  the 
invention  of  Giffard,  but  those  that  have  been  described, 
represent  steps  in  the  development  of  the  injector;  they 
have  been  selected  from  over  five  hundred  patents  granted 
by  the  United  States,  and  as  many  more  by  foreign  coun- 
tries. Many  changes  may  seem  to  be  merely  matters  of  de- 
tail,— yet  it  has  only  been  by  continued  experiment  with 
modification  of  minor  parts,  or  slight  changes  in  the  pro- 
portions or  arrangement  of  the  tubes,  that  progress  has  been 
made.  The  original  invention  was  conceived  upon  theoreti- 
cal principles,  the  correctness  of  which  has  been  so  signally 
demonstrated,  but  since  that  time  the  greater  part  of  the 
work  of  development  has  been  attained  only  by  close  atten- 
tion combined  with  critical  observation  in  experimental 
research. 


CHAPTER   III. 

DEFINITION  OF  TERMS — DESCRIPTION  OF  THE  IMPORTANT 
PARTS  OF  THE  INJECTOR — THEIR  FUNCTIONS. 

BRIEF  descriptions  have  already  been  given  of  the  differ- 
ent types  of  injectors  in  connection  with  the  history  of  the 
development,  but  as  the  technical  names  of  the  various  parts 
will  necessarily  enter  into  the  accounts  of  experiments  that 
follow,  the  definition  will  now  be  given  as  concisely  as 
possible. 

It  is  unfortunate  that  there  has  been  so  little  accord  in  the 
direction  of  injector  nomenclature;  patent  specifications  are 
sometimes  obscure  and  misleading,  and  the  terms  used  often 
confusing ;  even  the  names  ejector  and  injector  are  often 
appropriated  to  entirely  wrong  uses.  The  two  apparatus 
differ  in  principle  as  well  as1  in  essential  detail :  the  former 
can  operate  with  any  gas  or  any  liquid  in  conjunction  with 
any  other  gas  or  liquid,  while  the  action  of  the  injector  de- 
pends upon  the  expansion  and  condensation  of  a  gaseous 
fluid  acting  within  clearly  defined  limits.  Technically, 

An  Injector  is  an  apparatus  in  which  a  gaseous  jet 
impinges  and  is  condensed  by  a  fluid  mass  whose  final 
kinetic  energy  exceeds  that  of  a  jet  of  similar  form  and 
density  discharging  under  the  initial  pressure  of  the 
motive  jet. 

In  addition  to  the  use  of  condensible  gases,  the  existence 
is  required  of  certain  well  established  relations  between  the 
areas  of  the  discharging  and  the  receiving  nozzles,  which 
will  serve  for  a  clear  distinction  between  the  two  types  of 
apparatus : 

An  Injector  is  a  jet  apparatus  in  which   the  cross- 

25 


26  THE  GIFFARD  INJECTOR. 

section  of  the  discharge  nozzle  of  the  actuating  jet  is 
greater  than  that  of  the  receiving  or  delivery  tube. 

An  Ejector,  reverses  these  conditions,  and  the  gaseous 
or  liquid  discharge  will  freely  pass  through  the  delivery 
tube. 

Drawings  or  cuts  of  injectors  are  usually  made  with  the 
delivery  tube  discharging  toward  the  bottom  or  right  hand 
side  of  the  page,  and  the  terms  "  upper"  and  "lower  "  will 
be  thus  used.  The  index  letters  refer  to  the  various  figures, 
where  the  same  letter  always  is  used  on  the  same  tube. 

The  Delivery  Tube  (c]  is  that  tube  in  which  the  maxi- 
mum velocity  of  the  combined  mixture  of  water  and 
steam  is  attained,  and  subsequently  reduced,  by  means 
of  the  expanding  curves  and  increasing  cross- section,  to 
the  velocity  and  pressure  in  the  boiler  pipe. 
It  is  usual  to  indicate  the  nominal  size  of  the  injector  by 
the  mininum  diameter  of  this  tube,  as  the  amount  of  water 
delivered  is  chiefly  dependent  upon  this  dimension. 

The  Combining  Tube,  (£)  extends  from  the  upper  end 
of  the  delivery  tube  (c),  to  the  lower  end  of  the  steam 
nozzle  (a),  and  receives  its  name  from  the  combin- 
ing of  the  steam  with  the  water  that  occurs  within  its 
walls. 

The  Draft,  or  Suction  Tube,  (£')  facilitates  the  start- 
ing of  the  injector,  and  lies  between  the  upper  over- 
flow (d')  and  the  lower  end  of  the  steam  nozzle  (a) ;  its 
lower  diameter  is  usually  larger  than  the  minimum  dia- 
meter of  the  steam  nozzle. 

The  Steam  Nozzle  (a),  guides  and  directs  the  motion 
of  the  actuating  jet ;  its  effective  area  of  discharge  is 
often  varied  by  the  use  of  a  Steam  Spindle  (/),  in  order 
to  vary  the  amount  of  steam  used,  or  for  the  purpose  of 
lifting  the  feed  water. 

These  tubes  can  be  used  in  either  single  or  double  com- 
bination as  in  the  single  or  double  jet  injectors. 

Overflow,  (d~}  Primary  or  Lower,  a  narrow  annular 
vent  space  or  drilled  aperture,  placed  above  the  mini- 
mum diameter  of  the  delivery  tube,  permitting  free 


DEFINITION  OF  TERMS.  27 

outlet  for  the  water  and  steam  during  the  operation  of 
starting. 

Upper,  or  Supplemental  (af),  is  placed  nearest  to  the 
steam  nozzle,  and  often  made  of  sufficient  area  to  per- 
mit free  exit  for  the  full  discharge  of  the  steam  nozzle. 
Additional  overflows  are  frequently  used,  see  Fig.  6,  page 

2Z(d"  d'"). 

The  following  terms  are  used  as  descriptive  of  different 
classes  of  injectors  : 

Single  Jet  Injector,  one  in  which  a  single  set  of  com- 
bining and  delivery  tubes  is  used. 

Double  Jet. — An  injector  containing  two  sets  of  steam 
jet  apparatus,  of  which  the  first  or  lifting  set  receives 
the  feed  water  from  the  source  of  supply  and  delivers  it . 
to  the  second,  or  forcing  set,  from  which  it  receives  suf- 
ficient impulse  to  enter  the  boiler. 

Automatic  or  Re-Starting. — An  injector  that  is  able 
to  re-establish  automatically  the  continuity  of  the  jet, 
after  a  temporary  interruption  in  the  steam  or  water 
supply. 

Self-adjusting. — Applied  to  an  injector  in  which  the 
supply  of  water  is  automatically  adjusted  to  suit  the 
steam  supply  without  waste  at  the  overflow. 

Open  overflow  injector,  has  one  or  more  apertures  in 
the  combining  tube,  opening  into  one  or  more  overflow 
chambers,  that  may  be  closed  against  the  admission  of 
air  by  the  use  of  light  check  valves  opening  outward. 

Closed  overflow  injector,  can  only  start  by  means  of 
an  opening  or  vent  placed  beyond  the  delivery  tube, 
which  must  be  closed  in  order  to  divert  the  jet  into  the 
boiler. 
The  following  terms  relate  to  the  performance  : 

Maximum  capacity. — The  greatest  volume  or  weight 
of  feed  water  passing  through  the  delivery  tube  at  any 
given  steam  pressure  and  condition  of  feed.  It  is 
usually  measured  in  cubic  feet  or  pounds  per  hour  ;  the 
use  of  the  gallon  is  not  to  be  advised,  unless  its  value 
is  clearly  stated. 


28  THE  GIFFARD  INJECTOR. 

Minimum  capacity. — The  least  volume  or  weight  of 
water  as  above,  that  can  be  continuously  delivered 
against  boiler  pressure  without  waste  from  the  overflow. 
It  is  often  expressed  as  a  percentage  of  the  maximum 
capacity. 

Range  of  capacities. — The  difference  between  the 
maximum  and  minimum  capacities  expressed  in  terms 
of  the  maximum  capacity  ;  for  example,  if  the  max.  is 
300  cu.  ft.,  and  the  min.  is  200  cu.  ft.,  the  difference, 
100,  is  the  range,  which  is  33  per  cent. 

Overflowing  temperature. — Highest  admissible  tem- 
perature of  feed  water  with  which  the  injector  can  oper- 
ate without  wasting,  when  running  against  boiler 
pressure. 

Overflowing  pressure. — Under  given  conditions,  the 
highest  counter  pressure  against  which  the  injector  can 
run  without  wasting. 

Breaking  temperature,  Breaking  pressure. — Highest 
admissible  feed  temperature,  and  counter  pressure,  when 
the  waste  valve  is  closed.  Note. — With  closed  overflow 
injectors,  the  overflowing  and  breaking  temperatures 
and  pressures  are  in  most  cases  the  same. 

Efficiency. — This  may  be  based  upon  the  ratio  which 
the  total  heat  in  the  feed  water  and  in  the  steam,  bears 
to  the  heat  in  the  delivered  water  plus  the  heat  equiva- 
lent to  the  work  of  forcing  the  water  into  the  boiler. 
This  maybe  called  the  * '  Thermodynamic  Efficiency." 
Or,  the  ratio  of  the  work  performed  by  the  steam  in  forc- 
ing the  water  into  the  boiler,  to  the  total  energy  given 
out  by  the  steam  during  its  expansion  from  the  initial 
boiler  pressure  to  the  pressure  in  the  combining  tube. 
This  is  the  "  Mechanical  Efficiency."  Or,  it  may  be  ex- 
pressed in  terms  of  the  weight  of  water  delivered  per  unit 
weight  of  steam ;  this  is  a  very  simple  and  convenient 
methed  of  comparison,  and  is  thoroughly  practical. 
Note . — The  efficiency  is  often  measured  by  the  volume  or 
weight  of  water  delivered  per  unit  area  of  cross-section  of 
the  steam  nozzle  or  the  delivery  tube. 


DEFINITION  OF  TERMS.  29 

The  description  of  the  tubes  of  the  injector  will  be  taken 
up  in  the  following  order,  Delivery  tube,  Combining  tube, 
and  Steam  Nozzle,  the  theory  of  their  action  reviewed,  and 
practical  questions  considered  that  have  important  influence 
upon  their  design. 


CHAPTER    IV. 
THE  DEUVERY  TUBE. 

DESCRIPTION  I — EFFICIENCY  OF  VARIOUS  TYPES — EFFECT  OF  DIFFER- 
ENT SHAPES  AND  PROPORTIONS- 

THE  function  of  this  tube  is  to  change  the  kinetic  energy 
of  the  jet  to  potential,  with  the  least  possible  loss  :  or,  to 
transfer  the  energy  due  to  the  velocity  of  the  water  and  con- 
densed steam,  into  pressure  in  the  boiler  pipe. 

Of  all  its  dimensions,  that  of  the  minimum  diameter  is  the 
most  important,  for  it  is  from  this  base  that  the  dimensions 
of  all  the  other  parts  are  calculated.  The  use  of  this  di- 
ameter to  denote  the  size  of  the  instrument  was  first  sug- 
gested by  Giffard,  and  this  seems  to  be  the  most  rational 
method  that  can  be  used.  The  quantity  of  water  delivered 
by  an  injector  is  directly  dependent  upon  the  minimum  area 
of  this  tube,  and  under  the  same  conditions,  varies  with  the 
square  of  the  diameter ;  theoretically,  the  capacity  should 
be  equal  to  that  quantity  of  water  which  would  be  dis- 
charged from  a  similar  orifice  under  a  pressure  or  head  equal 
to  the  overflowing  pressure  of  the  jet,  which  is  always  in 
excess  of  the  pressure  carried  in  the  boiler.  If  there  were 
no  losses,  this  would  give  an  exact  method  of  determining 
the  weight  of  water  delivered,  and  as  it  is,  the  losses  referred 
to,  can  be  closely  approximated  ;  by  comparing  the  calcula- 
ted discharge  with  the  actual  test  of  the  injector,  a  per- 
centage of  efficiency  on  this  basis  can  be  readily  determined. 

This  basis  of  efficiency  has,  in  the  cases  of  all  single  jet 

injectors,  a  decided  value;   the  smaller  the  delivery  tube, 

the  smaller  can  be  the  other  orifices  of  the  injector,  reducing 

the  weight  of  steam  used,  and  rendering  its  operation  more 

30 


THE  DELIVERY  TUBE.  31 

economical.     As  an  example,  take  a  case  from  actual  prac- 
tice, from  which  the  efficiency  will  be  calculated. 

A  No.  8  Injector,  having  a  delivery  tube  8  millimetres 
in  diameter,  commences  to  waste  against  160  pounds 
(corrected)  back  pressure ;  the  delivery  temperature  is 
148  deg.  Fahr. 

The  height  of  a  column  of  water  at  this  temperature  that 
corresponds  to  the  pressure  of  one  pound  per  square  inch,  is 
2.354ft.,  (see  Table  II.,  page  43)  and  the  head  of  water 
equal  to  160  Ibs  is  2.354  X  160  =  376.64  ft.  This  gives  a 
velocity, 


if  =  \^2gh  —  8.024  V/j  =  8.024  V/376.  64  =  155.721  ft.  per  sec. 

The  area  of  the  delivery  tube  in  square  feet  is  0.000541068,' 
and  the  volume  that  would  be  discharged  from  this  tube 
under  this  head 

J55-72    X  0.000541068  x  3600  =  3°3-3T97  cu.  ft.  per  hour, 

which  must  be  equal  to  the  theorectical  quantity  of  water 
entering  against  that  pressure.  But  an  actual  test  showed 
that  251.5  cubic  feet  had  been  taken  from  the  feed  tank,  and 
that  the  weight  of  dry  steam  used  was  1304.5  pounds  ;  there- 
fore the  total  volume  passing  through  the  delivery  tube  per 
hour  was 


The  density  of  the  jet  was 


and  the  actual  velocity  of  the  jet 

155-721 


The  discharge  per  hour  per  square  millimetre  of  cross- 
section 

2728 

--  —  =5427  cubic  feet. 
50.2656 

This   gives  a  very  simple  means  of  comparing  different 
forms  of  injectors,  and   the  following  table  is  based   upon 


32 


THE  GIFFARD  INJECTOR. 


actual  tests  of  single  jet  locomotive  injectors  at  a  steam 
pressure  of  1 20  pounds  to  the  square  inch ;  no  Double  Jet 
Injectors  are  included,  as  the  conditions  under  which  the 
jet  passes  through  the  delivery  tube  of  the  two  types  are  not 
exactly  comparable : 

TABLE  I. 


NAME. 


Size. 


Garfield No.  7 

Mack No.  7 

Monitor No.  8 

Metropolitan No.  9 

Original  Giffard No.  8 

Sellers'  1876 No.  7 


Diameter 
Delivery 
Tube  in 
Milli- 
metres. 

Cu.  Ft.  per 
hour  per 
sq.  m.  m. 

7.26 

4.8876 

8.13 

3.8006 

8.28 

5.1258 

1075 

3-8555 

8.00 

4.4H2 

7.00 

5.6745 

TT'-Sf&i 

i     ' 

\ 

1 

\ 

1 

i 

1 

1 

The  principal  function  of  the  delivery  tube  has  already 
been  stated,  but  it  remains  to  show  the  means  by  which  the 
required  effect  is  produced.  A  section  of  a  tube  is  shown  at 
AB  in  Fig.  7,  where,  for  the  sake  of  clearness,  imagine  the 
entering  jet  divided  into  a  series  of  short  cylinders,  of  the 


THE  DELIVERY  TUBE.  33 

same  density  as  water  ;  also,  that  the  injector  is  working 
against  a  pressure  that  compels  the  tube  to  be  completely 
filled  with  water  ;  now,  if  the  tube  were  cut  off  at  the  section 
D,  the  jet  would  impinge  violently  against  the  wall  of  water 
in  front,  and  lose  its  energy  in  forming  eddies  and  disturb- 
ances, (see  Fig.  8),  in  proportion  as  its  velocity  is  greater 
than  that  of  the  water  ahead.  But  as  the  jet  passes  into  the 
tube,  the  cross  section  becomes  wider,  and  the  cylindrical 
form  changes  to  conical.  If  the  volume  contained  between 
any  two  sections  as  Ddf,  or  d'  d",  etc.  ,  be  the  same,  the  dis- 
tances a,  b,  r,  gradually  shorten  as  lateral  motion  toward  the 
walls  is  induced;  as  these  distances  shorten  an  increasing 
pressure  is  exerted  upon  the  surrounding  walls  and  upon  the 
particles  of  water  directly  in  front.  In  this  way  the  momen- 
tum of  the  jet,  which  is  at  the  maximum  at  D,  —  as  indica- 
ted by  the  highest  point  of  the  velocity  curve,  —  is  gradually 
reduced  to  that  of  the  feed  in  the  boiler  pipe.  By  refer- 
ence to  the  figure  the  pressure  and  velocity  of  the  jet  at 
any  point  can  be  determined  by  the  height  of  the  corres- 
ponding curve  above  the  base  line.  If  the  density  of  the 
jet  be  uniform,  its  velocity  at  any  point  of  a  given  tube 
can  be  obtained  by  dividing  the  actual  volume  passing 
through,  expressed  in  cubic  feet,  by  the  area  of  the  tube  in 
square  feet,  and  the  side  pressure  upon  the  walls  may  be 
calculated  by  the  following  formula  : 


144 


Where^,  —  pressure  required. 

P  —  pressure  in  boiler  pipe  at  end  of  the  delivery  tube. 
v  =  velocity  of  water  in  boiler  pipe. 
z/x  =  velocity  at  point  where  pressure  =  pv 
7  =  weight  of  one  cubic  foot  of  water  at  the  temperature 
of  delivery. 

It  is  of  course  advantageous  to  shape  the  tube  so  that  all 
the  energy  of  the  jet  can  be  utilized,  but  this  can  only  be 
done  by  applying  the  laws  governing  the  motion  of  fluids  ; 
the  effects  produced  by  improperly  shaped  tubes  may  be 
seen  by  the  following  tests,  where  the  same  conditions  ob- 
3 


34 


THE   GIFFARD   INJECTOR. 


tained  throughout,  both  as  to  steam  pressure  and  to  the 
volume  of  water  passing  through  the  injector.  The  first 
form  experimented  with  is  shown  in  Fig.  8,  which  corres- 
ponds to  the  mouth  or  entrance  of  a  delivery  tube,  as  if  the 
part  to  the  right  of  the  section  D,  in  Fig.  7  had  been  taken 
entirely  away;  the  result  of  this  was  that  the  injector  would 


only  force  against  a  pressure  of  35  pounds  without  overflow- 
ing, although  the  pressure  carried  in  the  boiler  was  65  pounds 
to  the  square  inch,  showing  the  enormous  proportion  of 
energy  dissipated. 

The  next  tube  was  made  cylindrical,  as  is  indicated  in 
Fig.  9.  Under  the  same  conditions  this  tube  showed  no  im- 
provement, as  only  25  pounds  was  reached;  it  was  then 


ffi'gJO. 


reamed  in  the  form  of  a  divergent  curve  approximating  in 
section  a  parabola  as  shown  in  Fig.  10,  and  the  effect  pf  the 
change  was  at  once  apparent  as  the  permissible  back  pres- 
sure rose  to  62  pounds ;  although  the  general  shape  was 
improved,  yet  the  tube  was  obviously  too  short  and  the 
curvature  too  great  for  the  high  velocity  at  which  the  jet 


THE  DELIVERY  TUBE. 


35 


was  moving,  and  the  tube  in  Fig.  n  was  substituted.  Its 
length  was  7.6  times  the  diameter,  and  developed  a  pressure 
of  88  pounds.  Further  change  in  the  proportion  raised  the 
pressure  against  which  the  jet  would  work  to  93  pounds, 
without  any  modification  of  any  of  the  other  parts  of  the 
injector,  or  increase  in  the  pressure  of  the  steam. 

It  has  long  been  known  that  the  divergent  tube  possessed 
the  peculiar  property  of  increasing  the  quantity  of  water 
that  would  flow  through  an  orifice  in  a  given  time,  and  this 
phenomenon  has  led  to  careful  experimental  work  by  Ber- 
nouilli,  Francis,  Brownlee,  and  others.  Francis  in  his  well- 
known  and  oft-quoted  Lowell  Hydraulic  Experiments,  found 
that  with  an  orifice  having  well  rounded  curves  of  approach, 
the  weight  of  water  discharged  under  a  constant  head  of 
1.36  feet,  could  be  increased  2.44  times  by  the  addition 


of  a  divergent  funnel  having  an  angle  of  5°  i'.  Brownlee, 
with  6  feet  head  of  water  increased  the  discharge  2.42 
times  by  the  use  of  a  tube  whose  included  angle  was  7°  5'. 
But  the  heads  of  water  and  the  velocities  of  the  jets  in 
both  these  cases  were  exceedingly  small  compared  with  those 
in  use  in  the  injector,  and  the  changing  conditions  in  the 
internal  action  of  the  jet  would  invalidate  any  positive  pre- 
diction regarding  the  effect  of  a  special  shape  of  divergent 
tube ;  yet  the  theory  under  which  such  tubes  may  be  de- 
signed is  interesting,  and  may  be  applied  in  a  limited  degree 
to  the  case  under  consideration,  under  the  assumption  that 
the  jet  has  the  same  density  as  that  of  water  ;  this  is  how- 
ever only  approached  in  those  types  of  injectors  which  are 
most  carefully  designed  and  constructed. 


36  THE  GIFFARD  INJECTOR. 

In  order  to  obtain  the  most  efficient  form  of  divergent 
tube,  it  has  been  suggested  by  Nagle  that  it  be  so  con- 
structed that  the  retardation  of  the  motion  of  the  jet  be 
made  uniform,  and  that  by  this  means  the  particles  of  water 
could  be  kept  in  equilibrium  and  internal  eddies  avoided. 
This  would  require  each  succeeding  section  of  the  delivery 
tube  to  be  increased  in  such  proportion  that  the  difference 
between  the  squares  of  the  velocities  of  any  two  equidistant 
sections  would  be  constant;  and  the  particles  of  water 
always  in  contact  with  its  walls.  It  should  be  remembered 
that  the  velocity  of  the  entering  jet  must  be  always  equal  to 
that  of  a  jet  of  similar  density  discharging  from  the  tube 
under  a  head  equal  to  the  difference  between  the  maximum 
pressure  against  which  the  jet  is  capable  of  working,  and 
the  internal  pressure  of  the  jet  at  the  time  of  entrance ;  it 
follows  therefore  that  the  absolute  pressure  of  the  jet  at 
this  point  would  influence  the  amount  of  water  passing 
through  the  tube,  if  the  construction  of  the  other  parts  of 
the  apparatus  were  such  as  to  permit  an  additional  quantity 
of  water  to  be  drawn  from  the  supply. 

The  reason  for  the  lowering  of  the  pressure  at  the  point 
of  minimum  diameter  may  thus  be  explained :  a  jet  of  water 
discharging  freely  into  air,  will  retain  its  full  velocity  and 
the  same  cross-secton  for  some  distance  beyond  the  mouth 
of  the  tube ;  but  by  reason  of  the  gradually  expanding 
curves  of  an  enveloping  tube,  the  jet  adheres  to  the  surroun- 
ing  walls  and  its  section  is  increased ;  but  the  energy  tends 
to  remain  the  same  as  before,  and  therefore  an  effort  is  ex- 
erted to  draw  the  preceding  particles  forward,  increasing 
their  velocity,  and  consequently  the  weight  of  water  dis- 
charged. If  the  tube  is  open  to  the  atmosphere,  a  lack  of 
equilibrium  results  as  air  is  drawn  in  at  the  lower  end,  but 
if  immersed,  the  effect  reacts  upon  the  particles  in  the  rear, 
and,  if  the  tube  is  correctly  proportioned,  a  perfect  vacuum 
will  be  formed  at  the  throat  of  the  tube. 

The  formulas  for  uniform  retardation  are  similar  to  those 
for  uniform  acceleration,  and  may  thus  be  expressed : 

Fbe  the  velocity  of  the  jet  and  D  the  diameter  of  the 


THE  DELIVERY  TUBE. 


37 


tube  at  the  throat  ;  let  v  and  d  have  the  same  values  at  the 
lower  end  of  the  tube  ;  then 


V  EP 

V  :  v  :  :  d*  :  D2  and  v  =  —.-?- 
a2 


(2) 


If  S  is  the  length  to  the  tube,  the  negative  acceleration,  or 
retardation  is 


or 


If  the  lower  end  of  the  tube  be  very  large  the  last  term  of 
(3)  becomes  so  small  that  it  may  be  neglected  without  sensi- 
ble error,  and  may  be  reduced  to 


The  equation  of  the  curve  of  the  half  section  of  a  tube 
that  would  fulfill  these  conditions  may  thus  be  found ;  in 
Fig.  1 2  let  A  B  be  the  half  section  of  a  delivery  tube  whose 
centre  line  is  Y  Y\  vertical  ordinates  denoted  by  x,  and 
abcissas  by  y  parallel  to  Y  Y\  substituting  2  x  for  d,  and  y 
for  S,  in  (4)  and  altering  its  form, 


By  way  of  example,  take  a  delivery  tube  8  millimetres  in 
diameter  and  the  length,  S1  taken  as  20.  (This  means  20 
spaces  of  equal  length  and  each  space  may  be  any  desired 


38  THE  GIFFARD  INJECTOR. 

distance  although  it  is  advantageous  to  make  the  total  length 
as  great  as  possible.)  The  entrance  velocity  of  the  jet  may 
be  assumed  as  156  feet  per  second,  and  the  final  velocity,  z/, 
as  o.  Substituting  in  (4)  gives  the  retardation,  and  (5)  re- 
duces to  __ 

*  =  4y  nro^y 


froni  which  the  diameter  can  be  determined  for  any  part  of 
the  tube  ;  for  the  following  values  of  _y,  d  has  been  calcula- 
ted, and  it  will  be  noticed  that  the  tube  widens  very  slowly 
at  first,  but  as  the  lower  end  is  approached  the  curve  becomes 
very  steep  and  finally  tangent  at  B. 

Forj  =    o  d  =    8.000 

=    5  =    8.590 

=  10  =    9.512 

=  15  =  10.912 

=  20  00 

Looking  at  these  formulas  from  a  practical  point  of  view,  it 
will  be  seen  that  they  depend  upon  the  value  of  V,  the  entrance 
velocity,  which  in  the  case  of  the  injector  must  vary  with 
every  steam  pressure  and  change  in  the  density  of  the  jet, 
although  it  is  at  the  maximum  capacity,  where  the  density 
most  nearly  approaches  unity,  that  the  full  efficiency  is 
needed.  Giffard  realized  the  advantage  of  using  differently 
shaped  tubes  for  high  and  low  pressure,  and  advised  the  use 
of  circular  arcs  whose  radii  in  the  former  case  were  300  times 
the  diameter  of  the  tube,  and  in  the  latter,  200  times.  This 
altered  the  proportion  of  the  tube  and  the  mean  angle  of 
divergence  of  the  tube  for  each  size  instrument,  but  this 
seems  for  many  reasons  to  be  theoretically  correct,  and  an 
improvement  upon  the  straight  taper  adopted  by  most  manu- 
facturers. 

The  change  in  the  velocity  of  the  jet  and  the  gradually 
increasing  pressure  upon  the  walls  of  the  tube  was  clearly 
shown  for  the  theoretical  case  assumed  in  Fig.  7  ;  as  an  illus- 
tration of  the  actual  changes  of  pressure  occuring  within 


THE  DELIVERY  TUBE.  39 

the  tube  under  different  conditions,  the  diagram  shown  in 
Fig.  13,  is  presented  through  the  courtesy  of  Wm.  Sellers 
&  Co.,  of  Philadelphia,  who  have,  ever  since  their  introduc- 
tion of  the  injector  into  the  United  States,  made  experi- 
mental work  an  important  part  of  their  system.  These  tests 
were  made  with  a  Self- Acting  Injector  of  1887,  at  65,  100, 
and  120  pounds  pressures.  The  delivery  tube  was  pierced 
at  four  points,  A,  B,  C,  D,  by  small  drilled  holes  one-six- 
teenth irfch  in  diameter,  upon  which  gauges  wrere  placed  to 
indicate  the  internal  pressure  of  the  jet.  Under  a  head  of 
30  feet,  water  was  allowed  to  discharge  through  the  tube 
and  the  vacuum  at  the  throat  of  the  tube,  as  indicated  by 
a  U  mercury  gauge,  was  found  to  be  27^  inches;  as  meas- 
ured by  actual  test  under  a  head  of  i8J^  feet,  the  amount 
of  water  passing  through  was  increased  a  little  over  42  per 
cent,  above  that  discharged  by  a  similar  orifice  without 
the  divergent  tube.  The  pipes  were  then  changed  so  that 
the  feed  water  could  be  lifted  from  a  tank  placed  below  the 
injector,  and  the  steam  turned  on;  the  pressures  observed 
were  plotted  on  the  vertical  lines  above  the  corresponding 
point  of  the  tube  and  connected  by  the  curved  lines  and 
marked  with  the  initial  steam  pressure.  The  rise  in  pres- 
sure wrhen  the  injector  is  running  at  its  maximum  capacity 
is  indicated  by  the  full  line,  the  minimum  by  the  dotted 
lines,  and  a  capacity  approximately  half-way  between,  by  the 
alternate  dot  and  dash. 

It  will  be  noticed  that  the  curves  for  the  maximum  capa- 
city rise  easily  from  the  low  pressure  at  the  throat  of  the 
tube  to  the  final  boiler  pressure  at  the  end,  distributing  the 
wear  very  evenly.  At  the  mean  capacity,  the  point  where 
the  greatest  abrasion  will  occur  is  evidently  at  the  section 
marked  C,  where  the  pressure  line  rises  suddenly  from  10" 
vacuum  to  95  pounds ;  at  other  steam  pressures  the  same 
peculiarity  was  noticed,  but  the  lines  were  not  added  to  the 
diagram  as  they  would  have  sacrificed  its  clearness.  At  the 
minimum  capacity,  the  wrear  is  chiefly  between  A  and  B,  as 
ma}r  be  seen  by  reference  to  the  dotted  curves.  These  facts 
constitute  a  strong  argument  in  favor  of  attaining  the  per- 


40 


THE  GIFFARD  INJECTOR. 


THE  DELIVERY  TUBE.  41 

feet  condensation  of  the  steam  within  the  combining  tube  and 
before  the  entrance  to  the  delivery  tube  is  reached,  and  one  of 
the  reasons  for  basing  the  efficiency  of  an  injector  upon  the 
amount  of  water  delivered  per  unit  of  area  of  delivery  tube. 

The  disadvantages  of  the  conical  tube  may  be  seen  from 
an  examination  of  the  light  full  line,  marked  120  pounds; 
the  abrupt  rise  in  pressure  against  the  walls  of  the  tube, 
even  on  the  maximum  capacity  and  when  all  conditions  are 
the  same  as  in  the  other  experiments,  shows  the  inferiority 
of  this  form  of  tube. 

The  various  causes  of  loss  of  energy  of  the  jet  can  be 
closely  approximated  in  the  most  important  cases  that  occur 
in  practice.  That  due  to  the  final  velocity  in  the  delivery 
tube,  and  impact  of  the  water  against  the  slowly  moving 
water  in  the  delivery  pipe,  can  be  found  from  the  expression, 


« 


Where  p  —  the  loss  in  back  pressure  in  pounds. 
z/j  =  the  velocity  in  the  boiler  pipe. 
dl  =  the  diameter  of  the  boiler  pipe. 
d  =-  the  diameter  of  the  lower  end  of  the  delivery  tube. 
7  =  the  weight  of  a  cubic  foot  of  water  at  the  temperature  of 
the  delivery. 

The  loss  in  head  due  to  the  friction  of  the  jet  upon  the 
walls  of  the  tube,  can  be  calculated  from  the  formula  for 
conical  pipes  ;  or,  if  curved,  by  using  the  nearest  angle  or 
angles  to  correspond.  This  loss  amounts  to  very  little,  com- 
pared with  the  pressures  carried,  and  this  equation  is  much 
simpler  than  that  for  tubes  formed  from  circular  or  para- 
bolic arcs.  In  Fig.  14  let 

p  =  loss  in  back  pressure  due  to  friction. 

V  =  velocity  of  jet  at  the  throat  of  tube. 

D  =  diameter  of  the  throat. 

d  =  diameter  of  lower  end  of  tube. 

6  =  included  angle  of  tube. 

ft  =  co-efficient  of  friction,  depending  upon  condition  of  tube. 

y  =  weight  of  one  cubic  foot  of  water,  as  before. 


.......  <„ 


42  THE  GIFFARD  INJECTOR. 

To  apply  these  two  formulas  to  an  actual  case,  take  a  de- 
livery tube  0.3"  at  the  throat,  3.6"  long,  and  a  taper  of  i  in 
12  in  diameter;  the  included  angle  is  4°  46".  Take  Fas 
156  feet  per  second,  and  /?,  as  0.0147  ;  d  is  found  to  be  0.6" ; 
substituting, 

_  i  |- 

whence, 

P  =  3-5  pounds  — 
and  from  formula  (7), 

i 


-  =  9-8  Ibs. 
2-354  V36          /     64.4 


This  loss  could  be  entirely  obviated  by  widening  the  end 
of  the  tube  in  easy  curves  to  the  diameter  of  the  boiler  pipe. 

The  co-efficient,  £,  will  depend  upon  the  condition  of  the 
walls  of  the  tube,  whether  smoothly  reamed  and  offering 
but  little  resistance  to  the  motion  of  the  jet,  or  whether 
abraded  by  constant  use  or  cut  in  circular  grooves  by  poor 
workmanship.  When  it  is  remembered  that  the  velocity  of 
the  jet  at  the  smallest  diameter  of  the  tube  corresponds  to 
that  attained  by  a  jet  of  the  same  density  issuing  under  a 
pressure  even  higher  than  that  in  the  boiler,  the  disadvan- 
tageous effect  produced  by  the  roughened  surfaces  of  the 
guiding  tube  can  be  easily  realized. 

This  leads  naturally  to  the  subject  of  the  wear  of  the  tube. 
From  what  has  been  said  regarding  the  distribution  of  inter- 
nal pressures,  the  points  where  the  greatest  wear  will  occur 
under  usual  conditions,  can  be  easily  seen.  The  presence  of 
grit  or  dirt  in  the  feed  water  will  cut  the  mouth  of  the  tube, 


THE  DELIVERY  TUBE. 


43 


and  enlarge  the  minimum  diameter,  acting,  by  reason  of  the 
high  velocity  of  the  jet,  like  a  continuous  grinding  cylinder ; 
but  it  is  further  down  in  the  tube  that  the  abrading  effect  is 
first  noticed,  near  the  place  marked  C  in  Fig.  13,  where  an 
annular  groove  is  often  worn  around  the  tube,  that  seriously 
impedes  the  motion  of  the  water ;  its  location  is  always  at 
that  point  where  the  pressure  suddenly  rises ;  as  the  cross- 
section  gradually  widens,  the  velocity  of  the  water  decreases, 
and  the  wear  is  less  noticeable.  Regarding  the  question  of 
repair,  it  may  be  said  that  this  tube  will  generally  be  the 
first  that  requires  replacing,  but  it  may  often  be  saved  by 
carefully  reaming  or  smoothing  out  the  roughened  places ;  if 
this  be  done,  the  minimum  diameter  may  be  somewhat  in- 
creased before  the  injector  will  cease  to  work  at  the  higher 
steam  pressures.  Its  power  at  low  steam  will  be  affected 
first  by  the  wearing  of  the  tube  at  this  point,  but  the  exercise 
of  a  little  judicious  management  will  often  prolong  the  life 
of  the  injector,  and  save  needless  substitution  of  new  parts. 
The  following  table  of  the  weight  of  a  cubic  foot  of  water 
at  different  temperatures,  and  the  head  of  water  in  feet  cor- 
responding to  a  pressure  of  one  pound  per  square  inch,  will 
materially  assist  the  calculation  of  the  performance  of  the 
injector  under  different  conditions.  It  has  been  compiled 
from  a  "Table  of  Comparative  Volumes,"  prepared  by  Mr. 
A.  F.  Nagle,  and  published  in  Proc.  Am.  Soc.  Mech.  Eng.; 
the  heads  of  water  are  based  upon  his  figures. 

TABLE  II. 


1 

Temp,      !     TiTp-vht    f        Head  in  feet       Temp.      !     w-j-t,!.    f 

Head  in  feet 

Water,  deg.,       I.wf^kA        =  to  i  Ib.  per  Water,  deff.      _  ."°  JL"!       !=  to  i  Ib  per 

Fahr. 

square  inch. 

|       Fahr'       | 

square  inch. 

39-1 

62.4250 

2.3067 

J30 

61.5320 

2.3402 

40 

62.42398 

2.3068 

140 

61.3432 

2-3474 

50 

62.40735 

2.3074 

150 

61.1413 

2.3552 

60 

62.36975 

2.3088 

160 

60.9266 

2-3635 

70 

62.31015 

2.3IIO 

170 

60.6988 

2.3723 

80 

62.2283 

2.3140 

180 

60.4608 

2.3818 

90 

62.1253 

2.3179 

190 

60.2128 

2-39*5 

IOO 

62.0033 

2.3224 

200 

59.9569 

2.4017 

no 

61.8626 

2.3277 

210 

59.6935 

2.4123 

120 

61.7053 

2.3336 

212 

59.6400 

2.4144 

CHAPTER  V. 

THE   COMBINING  TUBE. 

IN  describing  the  action  of  the  jet  within  the  delivery 
tube,  certain  theories  were  given  which  seemed  to  corre- 
spond closely  to  the  most  important  conditions  occurring  in 
actual  practice ;  unfortunately  the  action  of  the  steam  in  the 
combining  tube  is  not  so  definitely  understood,  and  the  most 
that  can  be  done  is  to  describe  the  phenomena  as  observed, 
and  deduce  a  few  general  conclusions. 

It  is  probable  that  more  experimental  work  has  been  re- 
quired to  perfect  this  tube  than  any  other  part  of  the  injec- 
tor, and  each  investigator  has  adopted  a  special  form  to  suit 
pre- determined  conditions,  that  seem  to  him  to  be  most  effec- 
tive. The  best  shape  can  be  decided  by  experiment  only, 
and  therefore  the  special  conditions  under  which  the  tests 
are  made  govern  the  result;  it  follows,  therefore,  that  there 
may  be  as  many  different  forms  as  there  are  manufacturers, 
and  to  a  great  extent  this  is  true,  each  type  of  injector  oper- 
ating more  or  less  successfully  under  a  certain  range  of  con- 
ditions. 

The  first  requisite  condition  that  the  tube  must  fill,  is  that 
the  water  must  be  sustained  during  the  impact  of  the  steam, 
and  the  second,  that  the  mixture  of  the  water  and  the  steam 
be  made  as  intimate  as  possible  in  order  that  complete  con- 
densation may  take  place  during  the  passage  of  the  jet 
through  this  tube ;  this  can  only  be  done  by  using  correct 
proportions  at  the  upper  end,  and  then  giving  to  the  lower  or 
convergent  part  the  same  shape  that  the  jet  would  assume 
during  the  process  of  condensation. 

It  is  this  tube,  in  great  measure,  that  governs  the  mechani- 
44 


THE   COMBINING    TUBE.  45 

cal  efficiency  of  the  injector.  Of  course  each  tube  has  its 
own  function,  yet  all  are  inter-dependent ;  but  the  process  of 
condensation,  that  differentiates  the  injector  from  other  simi- 
lar apparatus,  occurs  within  the  walls  of  this  tube.  In  the 
first  place,  assuming  a  constant  head  of  feed  water,  the 
cross-section  of  the  upper  end,  by  regulating  the  quantity  of 
water  that  may  enter,  determines  the  proportion  of  water  to 
steam  in  the  resultant  mixture,  and  the  temperature  of  the 
delivery.  The  vacuum  in  the  tube  is  dependent  upon  this 
temperature,  and,  therefore,  the  expansion  of  the  steam  and 
its  velocity  at  the  moment  of  impact  is  also  fixed ;  further, 
the  water  in  the  suction  pipe  is  drawn  into  the  tube  only  by 
the  internal  vacuum ;  the  influence  of  the  entrance  area  ex- 
tends also  to  the  velocity  of  the  feed  water,  as  it  approaches 
in  a  thin  sheet,  the  actuating  steam.  From  the  laws  of  im- 
pact, it  is  found  that  the  greater  the  difference  between  the 
velocities,  the  greater  will  be  the  loss  of  actual  energy  at  the 
moment  of  impact ;  as  the  wrhole  transfer  of  the  mechanical 
energy  of  the  steam  to  the  water  is  by  impact,  it  follows 
that  there  is  great  advantage  in  giving  to  the  entering  water 
the  highest  possible  velocity ;  this  can  only  be  obtained  by 
maintaining  the  pressure  in  the  combining  tube  as  low  as 
possible,  and  reducing  the  water  entrance  to  a  mininum. 
The  lower  this  pressure  the  higher  will  be  the  velocity 
of  the  entering  wrater,  and  the  greater  the  proportion  of 
water  to  steam  in  the  mixture. 

Secondly,  the  convergent  taper  or  curve  extending  from 
the  end  of  the  steam  nozzle  to  the  lower  overflow,  should,  in 
order  to  obtain  the  maximum  efficiency  from  the  injector, 
conform  closely  to  the  rate  of  condensation  of  the  steam,  and 
its  length  be  modified  for  every  variation  in  the  pressure 
of  the  steam  or  the  temperature  of  the  feed.  The  same  con- 
dition obtains  to  a  great  extent  with  the  water  entrance  area, 
whose  influence  upon  the  performance  of  the  injector  was 
detailed  in  the  preceding  paragraph.  It  was  appreciation 
of  these  facts  that  led  Giffard  and  the  early  experimenters  to 
lay  so  much  stress  upon  the  necessity  for  an  adjustable  com- 
bining tube.  The  advantage  of  this  feature  can  be  better 


46  THE  GIFFARD  INJECTOR. 

understood  if  we  suppose  an  injector  to  be  working  into  a 
boiler  under  normal  and  efficient  conditions,  lifting  the  feed 
water  one  foot  and  running  at  its  maximum  capacity ;  if  the 
steam  pressure  now  rise,  more  water  will  be  required  to 
condense  the  increased  flow  of  steam  and  preserve  the 
normal  condition  of  the  jet;  this  can  only  be  effected  by  in- 
creasing the  head  of  water  or  widening  the  distance  between 
the  steam  nozzle  and  the  combining  tube.  A  reduction  of 
pressure  would  evidently  require  a  reverse  movement,  for 
the  vacuum  within  the  tube  remaining  constant,  too  large  a 
quantity  of  water  would  enter  for  the  steam  to  force  through 
the  delivery  tube,  and  waste  would  occur  at  the  overflow. 
If  the  steam  pressure  fell  much  lower,  the  jet  of  steam 
would  not  have  sufficient  power  to  drive  the  accumulating 
mass  of  water  through  the  lower  end  of  the  combining 
tube,  and  the  continuity  of  the  jet  would  be  lost.  If  the 
openings  in  the  tube,  i.e.,  the  overflows,  were  large  enough, 
all  the  water  would  pass  out  through  the  waste  pipe  instead 
of  going  into  the  boiler,  even  though  the  sound  of  working 
be  the  same  as  that  with  which  the  engineer  might  be  famil- 
iar; on  the  other  hand,  if  the  overflows  are  small,  the 
injector  will  "break,"  or  "fly  off,"  and  steam  and  hot  water 
will  be  forced  down  into  the  suction  pipe. 

The  following  experiments  with  the  "  Little  Giant  Injec- 
tor ' '  illustrate  these  conditions  as  they  occur  in  practice ;  a 
No.  7  injector  was  started  at  90  pounds  steam  on  a  lift  of  one 
foot,  and  the  combining  tube  adjusted  for  the  full  capacity ; 
the  position  of  the  tube  was  measured  and  found  to  be  15 
millimetres  from  the  upper  end  of  its  stroke.  The  steam 
pressure  was  then  raised  to  120  pounds  and  the  temperature 
of  the  delivery  increased  from  136°  to  165°  ;  as  this  value  was 
entirely  too  high  for  efficient  performance,  the  tube  was  moved 
10  mm.  further  down  and  the  temperature  fell  at  once  to  148°. 

Starting  once  more  with  90  pounds  steam  and  delivery  at 
136°,  the  height  of  the  lift  of  the  feed  water  was  increased  to 
6  feet,  the  result  being  a  diminution  in  the  capacity  of  the 
injector  and  a  delivery  temperature  of  150°;  a  downward 
movement  of  the  combining  tube  of  10  mm. ,  brought  the 


THE  COMBINING   TUBE.  47 

capacity  up  to  the  standard,  and  reduced  the  delivery  tem- 
perature to  136°  again;  the  distance  between  the  tubes 
under  these  conditions  being  the  same  as  was  used  at  1  20 
pounds  when  lifting  the  feed  water  i  foot. 

The  following  table  gives  the  distance  between  the  com- 
bining tube  and  the  steam  nozzle  at  different  pressures,  both 
for  the  maximum  and  the  minimum  capacities  ;  the  height 
of  lift  is  i  foot  ;  it  will  be  noticed  how  much  variation  in  the 
position  of  the  tube  there  is  between  high  and  low  pressures. 

Distance  of  Combining  tube  from  upper 
end  of  Stroke. 


Steam  Pressure. 

Max.  Capacity. 

Min.  Capacity. 

120 

24    mm. 

3.5  mm. 

90 

15        " 

1.0      " 

60 

7      " 

0.5     " 

30  J-5    "  o-5     " 

The  wide  difference  between  the  position  of  the  combin- 
ing tube  at  30  and  at  120  pounds  steam  show  how  impossi- 
ble it  is  for  a  single  jet  injector  with  fixed  nozzles  to  work 
thoroughly  efficiently  over  a  large  range  of  pressures.  The 
only  means  by  which  this  is  attempted,  is  by  assuming  a 
certain  range  through  which  the  pressure  may  fluctuate, 
and  then  adjusting  the  combining  tube  so  that  the  injector 
will  work  into  the  boiler,  without  wasting  at  the  overflow 
and  at  its  maximum  capacity,  at  the  lower  limit  of  pressure  ; 
this  method  sacrifices  the  best  performance  of  the  injector 
at  higher  steam  pressures,  as  both  the  overflowing  tem- 
perature and  the  capacity  will  be  lower  than  if  the  tubes 
were  differently  adjusted.  In  the  previous  example,  if  the 
combining  tube  is  set  for  a  steam  pressure  of  40  pounds,  the 
adjustment  would  be  correct  for  the  minimum  capacity  at 
120  pounds;  therefore,  as  the  pressure  was  increased,  the 
efficiency  of  the  instrument  would  diminish,  and  a  less  pro- 
portion of  water  be  delivered  per  pound  of  steam. 

This  demonstrates  the  superiority  of  the  adjustable  or  self- 
adjusting  form  of  injector  over  the  fixed-nozzle  type  for  use 
in  all  places  where  the  steam  pressure  is  subject  to  much 
fluctuation  ;  the  correct  ratio  between  the  weight  of  the 
water  and  the  weight  of  the  steam  can  always  be  maintained 


48  THE  GIFFARD  INJECTOR. 

in  the  former  case,  and  the  capacity  increased  with  the 
steam  pressure;  even  though  a  throttling  valve  may  be 
placed  in  the  feed  pipe,  the  results  obtained  where  there  is 
considerable  range  of  pressure,  as  in  locomotive  service, 
cannot  be  as  satisfactory  as  with  the  other  method  of  regu- 
lation. 

The  form  of  the  combining  tube  'as  determined  by  various 
experimenters  differs  greatly ;  in  the  tests  of  the  Irwin  In- 
jector by  a  committee  of  the  Franklin  Institute,  in  1879,  a 
tube  was  used  whose  length  was  only  four  times  the  diame- 
ter of  the  delivery  tube ;  this  is  a  great  contrast  to  that  of 
the  exhaust  injector,  where  the  ratio  is  18  to  i ;  this  cor- 
responds to  the  usual  practice  for  high  pressure  steam, 
where  the  increased  quantity  of  heat  requires  provision  for 
its  absorption,  and  this  can  be  best  accomplished  by  length- 
ening the  tube,  and  giving  better  opportunity  for  intimate 
mixture  between  the  water  and  the  steam ;  with  the  exhaust 
injector  this  is  necessary  on  account  of  the  large  volume  of 
steam  used,  which  requires  ample  time  for  condensation,  for 
the  temperature  of  the  delivery  is  higher  than  that  of  a  well 
designed  live  steam  injector  working  at  150  pounds. 

The  advantages  of  the  adjustable  combining  tube  for  vary- 
ing the  water  area  are  further  increased  if  this  adjustment  be 
made  automatic  and  effected  by  the  action  of  the  jet  itself; 
that  this  has  been  done,  was  shown  in  the  description  of  the 
self-adjusting  injector,  accompanying  Fig.  3  ;  in  this  case  the 
automatic  action  was  described  as  effected  by  the  influence 
of  the  jet  passing  the  overflow  space,  and  it  was  shown  that 
the  combining  tube  was  moved  forward  by  the  partial 
vacuum  produced  by  incomplete  condensation  of  the  steam, 
or  backward  by  the  pressure  due  to  excess  of  water  in  the 
feed  chamber.  It  is  interesting  to  note  the  action  of  the 
steam  upon  the  upper  end,  which  is  as  follows:  the  dis- 
charging jet,  striking  against  the  film  of  water  on  the  inside 
of  the  tube,  tends  to  impel  it  forward,  while  the  rapid  con- 
densation of  the  steam  produces  a  reactive  effect  which 
draws  the  tube  backward  toward  the  steam  nozzle,  and  these 
two  pressures  almost  exactly  balance  ;  but  as  this  action  only 


THE   COMBINING    TUBE.  49 

occurs  in  the  central  conical  part,  the  rest  of  the  piston  head 
receives  the  positive  or  negative  pressure  in  the  feed  pipe, 
just  as  the  lower  end  is  acted  upon  by  the  pressure  in  the 
confined  overflow  chamber  ;  this  has  been  found  to  be  true 
by  placing  a  vacuum  gauge  upon  the  overflow,  and  noting 
its  reading  as  the  height  of  the  lift  increases  ;  it  is  found 
that  the  two  readings  correspond  almost  exactly,  and  that 
the  tube  floats  between  two  balancing  cushions,  ready  to 
respond  to  any  change  in  the  governing  conditions. 

In  calculating  the  performance  of  an  injector,  it  is  often 
desirable  to  know  the  vacuum  within  the  combining  tube. 
This  may  be  determined  by  allowing  water  under  a  constant 
head  to  flow  freely  through  the  tube,  special  care  being 
taken  to  see  that  the  feed  valve  is  full  open  and  that  the 
upper  overflow  is  large  enough  to  permit  free  discharge  for 
all  the  water  that  will  enter  ;  the  best  proof  of  this  is  to  dis- 
connect the  steam  branch  and  observe  if  the  water  rises  into 
the  steam  nozzle  ;  if  it  does,  the  overflow  space  is  too  small 
to  permit  a  free  discharge.  If,  however,  this  test  is  satisfac- 
tory, weigh  the  quantity  of  water  flowing  through,  and  then 
connect  the  steam  pipe  and  admit  steam  ;  without  altering 
the  position  of  the  water  valve,  regulate  the  supply  of  steam 
until  the  injector  will  just  run  without  wasting,  and  note  the 
new  weight  of  water  ;  these  two  values  will  bear  the  same 
relation  to  each  other  as  the  square  roots  of  the  heads. 

Here  is  an  actual  test  of  an  exhaust  injector,  taken  under 
rather  unfavorable  conditions  as  the  feed  water  was  76  de- 
grees: under  a  constant  pressure  of  4.25  pounds  or  9.817 
feet,  1987.5  pounds  of  water  flowed  through  the  injector; 
with  the  steam  valve  opened  and  working  into  boiler, 
the  weight  increased  to  3887.5  pounds,  due  to  the  vacuum 
in  the  combining  tube  Therefore, 


5  :  3887.5  :  :  ^79.817  :  ^37.48  =  total  head. 
Subtracting, 

37.48  —  '9.817  =  27.663  feet  vacuum,  =  24^"  mercury, 

which  is  the  value  required. 


50  THE  GIFFARD  INJECTOR. 

The  average  vacuum  within  the  tube  cannot  vary  much 
from  that  corresponding  to  the  mean  temperature  of  the  feed 
and  the  delivery,  yet  the  pressure  at  the  point  where  the 
water  enters  is  much  lower ;  it  is  there  that  the  water  is  the 
coldest,  and  the  outside  edges  of  the  discharging  jet  obtains 
its  fullest  expansion.  This  will  be  shown  in  the  diagram 
showing  the  discharge  from  the  steam  nozzle  (see  page  54), 
and  described  under  that  heading.  It  is  interesting  to  de- 
termine as  closely  as  possible  the  average  pressure  within 
the  tube,  for  it  is  only  by  this  means  that  the  final  expan- 
sion of  the  steam  can  be  found,  and  its  terminal  velocity 
calculated. 

So  far  it  has  only  been  assumed  that  there  was  a  partial 
vacuum  in  the  tube.  As  it  is  obvious  that  steam  is  always 
condensed  when  coming  in  contact  with  a  body  whose  tem- 
perature is  lower  than  that  corresponding  to  its  pressure,  so 
it  is  possible  that  steam  may  be  condensed  in  an  injector  tube 
even  when  the  entering  water  is  above  212  degrees.  This  is 
most  nearly  approached  in  the  double  jet  injector,  where 
the  water  entering  the  combining  tube  of  the  second  set  of 
tubes  is  often  as  high  as  180  or  190  degrees,  when  the  tem- 
perature of  the  supply  is  150.  It  is  very  probable  that  in  this 
case  only  a  very  small  percentage  of  the  steam  from  the 
second  steam  nozzle  is  condensed,  but  sufficient  to  permit 
the  combined  jet  of  steam  and  water  to  contract  sufficiently 
to  pass  through  the  narrowest  section  of  the  delivery  tube. 
The  velocity  with  which  the  water  enters  the  tube  is  also 
mucji  increased,  for  the  pressure  between  the  two  sets  of 
tubes  rises — at  1 20  pounds  steam — to  40  or  45  pounds ;  so 
that  the  work  required  of  the  second  steam  jet  is  not  very 
great. 

There  is  no  doubt  that  if  an  indefinite  amount  of  time 
were  given  for  the  condensation  of  the  steam,  feed  water 
could  be  taken  at  any  temperature  below  that  of  the  steam, 
but  it  must  be  remembered  that  the  actual  time  of  contact 
is  only  that  required  to  traverse  the  tube,  and  that  the  mix- 
ing can  only  be  between  the  two  conical  exposed  surfaces  ; 
therefore,  if  the  difference  in  temperature  be  small,  the  trans- 


THE  COMBINING    TUBE.  51 

mission  of  heat  will  be  correspondingly  slow,  and  the  volume 
of  the  steam  will  not  be  reduced  enough  to  enter  the  delivery 
tube.  The  effect  would  be  similar  to  that  of  an  air  jet  dis- 
charging into  a  mass  of  water — a  dispersion  and  atomizing 
of  the  whole  mass.  It  is  evident,  therefore,  that  the  thinner 
the  sheet  of  entering  water  and  the  lower  the  final  velocity 
of  the  jet,  the  greater  will  be  the  efficiency  of  the  injector. 

For  each  special  purpose  the  tube  has  to  be  designed,  and 
the  form  best  adapted  for  high  temperature  is  not  that  which 
is  best  suited  for  low  pressures  of  steam  or  for  high  lifts,  so 
that  the  shape  adopted  for  ordinary  practical  results  is 
usually  the  mean  for  the  conditions  under  which  the  injector 
is  to  operate,  regarding  which  each  designer  is  apt  to  have 
his  own  opinion. 

Temperatures  as  high  as  162  degrees,  and  variations  of 
capacity  up  to  75  per  cent,  have  been  obtained  in  experi- 
mental work  by  forms  of  the  Sellers'  Fixed  Nozzle  Injector 
with  varied  forms  of  tube,  neither  of  which  the  writer  be- 
lieves has  ever  been  exceeded  by  any  other  styles  of  injector 
with  which  he  is  familiar. 

The  advantage  of  maintaining  the  feed  water  pure  and  free 
from  lime  and  dirt  is  more  apparent  in  the  case  of  the  com- 
bining tube  than  with  any  other  part  of  the  injector ;  as  the 
specific  gravity  of  sand  and  grit  is  greater  than  that  of  the 
water,  all  foreign  particles  are  driven  with  great  force 
against  the  walls  of  the  tube  by  the  impact  of  the  steam. 
The  tendency  is  not  only  to  enlarge  the  diameters  at  differ- 
ent points,  but  also  to  change  the  shape  by  wearing  and 
grinding  off  all  shoulders  against  which  the  jet  can  strike ; 
soft  spots  in  the  brass,  caused  by  unequal  mixing  of  the 
metal  before  casting,  soon  show  the  effect  of  abrasion,  and 
this  introduces  a  diagonal  motion  to  the  particles  that  wear 
depressions  upon  the  opposite  side.  Tubes  that  have  been 
used  with  impure  water  show  this  feature  very  strongly,  and 
the  conical  shape  is  frequently  changed  to  that  of  two  cylin- 
ders, connected  by  an  abrupt  shoulder.  The  force  of  the 
impact  of  the  jet  of  steam  is  so  severe,  that  a  tube  with  walls 
Ty  thick  was  found  to  have  a  pocket  }i"  deep  worn  in  it  at 


62  THE  GIFFARD  INJECTOR. 

the  end  of  the  steam  nozzle,  and  the  outside  was  considera- 
bly bulged  by  the  continuous  blows  it  had  received. 

But  with  pure  water,  a  well  designed  tube  will  last  a  long 
time,  and  in  railroad  service,  where  so  many  injectors  are 
employed,  the  choice  of  the  water  supply  should  take  into 
consideration  not  only  the  chemical  analysis,  but  also  the 
percentage  of  impurities  mechanically  mixed  with  it;  in 
many  cases  these  impurities  are  almost  invisible  to  the  naked 
eye,  and  it  is  only  by  careful  nitration  that  the  trouble  can  be 
remedied.  On  many  of  the  railroads  of  France,  this  system 
of  purification  is  carried  out  very  perfectly,  and  the  effect  is 
apparent  not  only  in  a  reduction  in  the  cost  of  repair  to  the 
locomotive  boilers,  but  also  in  the  longer  life  of  the  injectors. 


CHAPTER   VI. 

THE  STEAM    NOZZLE. 

THE  advantage  of  obtaining  the  highest  velocity  of  the 
steam  at  the  instant  it  strikes  the  water  has  already  been 
shown,  so  that  the  great  importance  of  obtaining  the  best 
shape  for  the  nozzle  which  guides  the  discharge  of  the  actu- 
ating jet,  is  at  once  apparent. 

As  it  was  assumed  in  the  earliest  experiments  that  the 
discharge  of  gases  followed  the  same  laws  that  govern  in- 
elastic fluids,  the  steam  nozzles  of  the  first  injectors  were 
made  with  a  gradual  convergent  taper,  and  it  was  not  until 
1869  that  the  form  was  improved  by  the  application  of  a 
divergent  flare,  that  permitted  expansion  of  the  steam  within 
the  limits  of  the  tube.  The  effect  of  this  change  upon 
inelastic  fluids,  like  water,  would  have  been  to  increase  the 
volume  discharged  and  diminish  the  terminal  velocity ;  but 
with  steam,  air  or  other  gases,  the  gradual  lowering  of  the 
pressure  as  the  jet  traverses  the  tube,  gives  an  increase 
in  volume  and  expansion  in  the  direction  of  the  flow,  which 
augments  the  velocity  of  the  particles  of  the  fluid,  while  the 
weight  discharged  remains  unchanged. 

In  order  to  demonstrate  more  clearly  the  great  difference 
between  the  discharge  of  gases  and  liquids,  some  experiments 
will  be  described  that  were  made  with  tubes  of  different 
forms,  using  steam  under  pressures  of  120  and  60  pounds 
(gauge).  Sketches  and  instantaneous  photographs  were 
taken  of  jets  of  steam  discharging  into  the  air,  and  the 
form  of  the  jet  and  the  direction  of  the  motion  of  the 
particles  were  carefully  noted.  The  results  are  given  in 
Fig.  15,  which  accurately  represents  the  external  form  as- 

53 


54  THE  GIFFARD  INJECTOR. 

sumed  by  the  jets,  although  it  does  not  show  the  change 
from  transparency  to  whiteness  that  occurs  shortly  after  the 
steam  •  leaves  the  nozzle.  Four  styles  of  tubes  are  given : 

1.  A  convergent  nozzle  or  short  cylinder. 

2.  An  aperture  in  a  thin  plate. 

3.  A  divergent  tube,  straight  taper. 

4.  A  divergent  tube,  curved  taper. 

FIG.   15. 


DISCHARGING   TUBES 

STEAM. 


Divergent^- 
Curve 


The  first  tube  represents  the  shape  that  would  be  used  to 
produce  a  solid  water  jet  at  a  high  velocity,  and  is  similar  to 
the  earliest  form  of  the  steam  nozzle.  The  second  is  a  thin 
diaphragm,  or  any  orifice  where  the  thickness  of  the  walls  is 
small  compared  with  the  width  of  the  opening.  The  third 
is  shaped  like  a  divergent  cone,  widening  in  the  direction  of 


THE  STEAM  NOZZLE.  65 

the  flow.     The  fourth  has  the  same  dimensions,  but  expands 
in  Curved  lines  from  the  throat  to  the  lower  end. 

In  all  these  experiments,  the  jet,  after  leaving  the  end  of 
the  nozzle,  was  almost  invisible  for  a  distance  of  two  or  three 
diameters,  and  of  a  pale  bluish  color,  marked  with  light 
lines  of  white,  apparently  produced  by  the  entrained  parti- 
cles of  water.  Beyond  the  transparent  portion,  the  jet  ex- 
panded to  a  much  larger  diameter,  became  white  on  the 
surface,  and  was  finally  condensed  by  the  cooling  effect  of 
the  air. 

The  difficulty  with  the  first  two  tubes  is  that  they  permit 
immediate  diametral  expansion  of  the  steam,  instead  of 
confining  it  and  compelling  expansion  in  the  direction  of 
motion.  A  transparent  envelope  is  formed,  three  or  four 
times  the  size  of  the  orifice,  through  which  the  central  jet, 
discharging  at  somewhat  higher  velocity,  can  be  distinctly 
seen.  This  swelling  of  the  jet  is  due  to  the  fact  that  the 
internal  pressure  at  the  moment  of  discharge  is  greater  than 
that  of  the  medium  into  which  it  is  flowing ;  it  is  most  ap- 
parent in  No.  2,  because  in  this  tube  the  internal  pressure 
of  the  steam  at  the  terminal  section  is  the  highest,  and  in 
all  cases  is  more  marked  with  high  than  with  low  steam. 
In  the  divergent  nozzle,  the  terminal  pressure  is  the  same 
as  that  of  the  atmosphere ;  if  it  were  higher,  there  would 
be  the  same  enlargement  that  occurs  in  the  previous  cases, 
and  if  lower,  a  contraction  would  be  caused  by  the  pressure 
of  the  air.  In  these  two  nozzles,  the  direction  cf  discharge 
of  the  particles  is  almost  exactly  parallel  with  the  axis,  and 
therefore,  all  the  energy  of  the  steam,  except  the  slight  loss 
due  to  friction  against  the  walls,  is  utilized  for  augmenting 
the  velocity. 

To  find  the  velocity  of  discharge  a  knowledge  of  the  in- 
ternal condition  of  the  jet  is  essential ;  during  the  move- 
ment of  the  steam  toward,  and  through  the  tube,  there  must 
be  a  reduction  in  its  pressure,  and  a  corresponding  increase 
in  volume.  If  then,  the  area  of  the  nozzle  at  different  sec- 
tions is  known,  it  will  be  necessary  to  find  the  pressure  at 
those  points  in  order  to  determine  the  volume  or  density 


56  THE  GIFFARD  INJECTOR. 

from  which  the  velocity  may  be  calculated.  This  was  done 
when  the  injector  was  forcing  water  into  the  boiler,  and  also 
when  the  steam  was  discharging  freely  into  the  air,  by 
inserting  a  small  tube  along  the  axis  of  the  nozzle,  and 
observing  the  indications  of  a  gauge  placed  on  its  outer  end. 
Communication  was  made  with  the  interior  of  the  jet  by 
means  of  a  small  hole  drilled  through  the  tube,  so  that  by 
sliding  the  tube  backward  or  forward,  the  internal  pressure 
of  the  jet  could  be  obtained  within  or  beyond  the  limits  of 
the  nozzle,  either  when  the  injector  was  working,  or  during 
free  discharge.  By  this  means  the  pressure  within  the  trans- 
parent portion  of  the  jet  was  ascertained,  and  the  fall  of 
pressure  during  condensation.  The  experiment  was  also 
tried  of  drilling  minute  holes  through  the  steam  nozzle 
normal  to  the  jet,  and  reading  the  gauge  directly,  but  by  this 
method  observations  were  restricted  to  the  limits  of  the  nozzle 
and  could  not  be  obtained  when  the  injector  was  in  action. 

The  results  of  these  investigations  are  shown  in  Fig.  16, 
where  A  is  the  steam  nozzle,  B  the  combining  tube,  f  the 
hollow  spindle  with  transverse  hole/"',  by  which' the  pressure 
was  communicated  to  the  gauge.  The  intersections  of  the 
vertical  lines  with  the  curved  lines  in  the  diagram  indicate 
the  pressure  at  the  respective  points  of  the  nozzles ;  the 
horizontal  lines  represent  pressure  above  or  below  the  at- 
mospheric line.  Observations  were  made  at  60  and  120 
pounds  gauge  pressure,  the  full  line  showing  the  conditions 
when  the  injector  is  running,  and  the  dotted  line  when  the 
steam  nozzle  is  discharging  into  the  air. 

Considering  first  the  case  where  the  injector  is  working, 
it  will  be  noticed  that  as  the  particles  of  steam  approach  the 
entrance  to  the  nozzle,  the.,  pressure  falls  in  easy  curves  until 
the  smallest  part  of  the  tube  is  reached,  when  the  descent  is 
more  abrupt,  but  approaching  the  usual  form  of  expansion 
as  shown  by  the  indicator  card  of  a  steam  cylinder.  Just 
bej^ond  the  end  of  the  steam  nozzle,  at  the  line  a' a1 ',  the  prox- 
imity of  the  feed  water  causes  a  quick  fall  of  pressure  that 
is  only  partially  recovered  during  its  passage  through  the 
combining  tube. 


THE  STEAM  NOZZLE. 


57 


These  pressures  of  22"  for  120  pounds,  and  24"  for  60 
pounds,  are  found  at  the  centre  of  the  jet;  that  due  to  the 
actual  contact  of  the  feed  water  with  the  steam  envelope 
would  approach  more  nearly  a  perfect  vacuum. 

FIG.   16. 


Jltmo!. 


DIAGRAM 

Pressure  in  $teawJfozzle 

a,t 


Jtyvctor  tvorhng'. 


1  1  V 

i     1         i^l  • 


Turning  now  to  the  freely  discharging  steam,  it  wrill  be 
observed  that  during  passage  through  the  nozzle,  the  lines 
for  the  two  conditions  almost  overlie,  and  probably  would, 


58  THE  GIFFARD  INJECTOR. 

if  all  slight  errors  of  observation  could  be  excluded ;  this 
seems  singular  when  it  is  considered  that  in  one  case  the 
steam  is  discharging  into  a  partial  vacuum,  and  in  the  other, 
into  the  air  ;  beyond  the  line  a' a  the  curves  separate,  yet 
both  pass  below  the  atmospheric  line,  the  curve  of  free  dis- 
charge rising  and  falling,  owing  to  the  unstable  equilibrium 
of  the  j  et.  Under  1 20  pounds  initial  pressure  the  j  et  emerging 
from  the  tube  at  9  pounds  pressure,  expands  to  atmospheric, 
and  then  by  internal  condensation,  n"  vacuum  is  reached, 
but  is  soon  overcome  and  equilibrium  established.  This 
peculiar  phenomena  of  alternate  rising  and  falling  of  the  in- 
ternal pressure  is  thoroughly-  borne  out  by  the  external 
appearance  of  the  jet,  as  it  presents  the  appearance  of 
having  nodes  separated  by  swelling  curves.  The  60  pound 
pressure  line  shows  that  the  steam  leaves  the  nozzle  at  a 
pressure  of  4"  vacuum,  and,  therefore,  contracts  instead  of 
showing  the.  surrounding  envelope,  characteristic  of  the 
other  case. 

From  the  correspondence  of  the  curves  showing  the  fall 
of  pressure,  under  both  conditions  of  discharge,  it  appears 
that  the  outflow  is  unaffected  by  the  pressure  in  the  receiv- 
ing chamber;  when  the  injector  was  working  at  120  pounds, 
the  pressure  beyond  the  end  of  the  steam  nozzle  was  22" 
vacuum,  and  in  the  other  case,  14.7  pounds,  yet  the  con- 
ditions within  the  limits  of  the  nozzle  were  almost  precisely 
the  same.  If  the  experiments  were  carried  still  further,  and 
the  weight  of  steam  determined  that  would  pass  in  a  unit  of 
time  through  an  orifice  in  a  reservoir  in  which  the  initial 
pressure  was  maintained  constant,  while  the  pressure  in  the 
receiving  tank  was  increased  from  a  vacuum  up  to  the* 
upper  limit  of  pressure,  it  would  be  found  that  the  rate  of 
flow  would  be  practically  constant  until  the  counter  pressure 
was  raised  to  -f$  of  the  initial.  It  is  true  theoretically, 
and  has  been  also  proved  by  careful  experiment,  that  this 
value  of  T%,  corresponds  closely  to  the  relation  of  pressures 
that  will  give  maximum  flow,  although  the  actual  in- 
crease above  the  weight  discharged  against  atmospheric 
pressure  is  small.  At  120  pounds  gauge  pressure,  for  ex- 


THE  STEAM  NOZZLE. 


59 


ample,  a  little  more  steam  will  be  discharged  against  66 
pounds  than  there  would  be  into  the  air,  for,  taking  the 
absolute  pressures  to  which  this  ratio  applies,  (120  -f  15)  X 
0.6  =  8i.=  the  absolute,  or  81  —  15  =  66.0  =*  the  gauge 

FIG.   17. 


pressure.  As  an  explanation  of  this  peculiarity  of  the  jet, 
Rankine  has  suggested  that  there  is  always  a  limiting  sec- 
tion at  which  the  internal  pressure  is  0.58  of  the  initial,  and 
until  that  value  is  exceeded  at  a  lower  part  of  the  jet,  the 
flow  will  not  be  reduced. 


60  THE  GIFFARD  INJECTOR. 

With  apertures  in  thin  plates,  like  No.  2,  Fig.  15,  or  short 
cylindrical  tubes,  the  limiting  section  is  found  directly  at 
the  opening ;  but  with  many  of  the  steam  nozzles  as  designed 
for  injector  use,  it  is  a  little  in  the  rear  of  the  minimum 
diameter ;  this  is  true  even  when  the  tube  may  be  designed 
to  permit  immediate  free  expansion,  as  shown  in  Fig.  17 
where,  although  the  pressure  at  the  smallest  diameter  is 
below  0.58  of  the  initial,  the  velocity  at  that  point  is  nearly 
constant.  The  diagram  shows  a  half  section  of  a  nozzle 
divided  by  vertical  dotted  lines  that  pass  through  minute 
holes  that  were  drilled  for  the  purpose  of  obtaining  the 
pressure  of  the  jet  by  means  of  an  ordinary  gauge.  Readings 
were  taken  at  the  different  steam  pressures,  and  the  results 
plotted  under  the  respective  parts  of  the  tube  The  pressure 
lines  are  similar  to  those  in  Fig.  16,  and  indicate  the  rate  of 
expansion  of  the  steam  while  traversing  the  nozzle.  The 
upper  curves  are  for  the  velocity,  and  are  calculated  from 
the  observed  pressures ;  these  curves  almost  overlie  through- 
out their  whole  length,  and  probably  would,  if  the  flare  of 
the  nozzle  were  still  further  expanded. 

The  throat  pressures,  ratios  and  velocities  are  as  follows : 

Initial  Pressure,          Throat  Pressure,  Velocity  at  Throat. 

Absolute.  Absolute.  Ratio.  Feet  per  Sec. 

135  698  0-5I7  1 612.0 

45  22.8  0.508  1603.0 

Although  there  is  a  difference  of  95  pounds  between  the 
extreme  initial  pressures,  there  is  only  a  difference  of  9  feet 
in  the  two  velocities.  It  is  possible  that  the  orifice  by  which 
the  pressure  was  recorded  on  the  gauge  in  these  experiments, 
was  a  little  below  the  limiting  section— probably  not  more 
than  T^J-  inch — as  the  smallest  change  in  its  position  gives 
a  wide  variation  in  the  pressures. 

The  ordinary  type  of  injector  steam  nozzle  gives  slightly 
different  results,  for  the  divergent  taper  is  straight  and  does 
not  allow  as  great  an  amount  of  transverse  expansion,  so 
that  the  ratio  of  the  throat  pressure  to  the  initial  pressure  is 
not  constant.  With  a  tube  having  a  divergent  flare  of  i  in 
6  in  diameter,  the  following  results  were  obtained : 


THE  STEAM  NOZZLE.  61 

Absolute  Pressure. 
Initial.  Throat.  Ratio.  Velocity  in  Throat. 

135  82.0  0.606  1407 

105  61.5  .585  1448 

75  42  .559  U91 

45  24.5  .546  1504 

In  this  case,  the  nozzle  was  formed  with  easy  curves  of 
approach  to  a  short  cylindrical  portion  whose  length  was  o.  3 
the  diameter  arid  into  which  the  gauge  hole  was  drilled; 
from  this  point  the  tube  widened  with  a  taper  of  i  in  6. 
This  tube  corresponded  to  a  form  of  steam  nozzle  exten- 
sively used  in  injector  service,  and  proves,  from  the  fact  that 
neither  the  pressure  ratios  nor  the  velocities  are  constant, 
that  the  actual  rate  of  expansion  is  not  similar  to  that  of 
free  discharge,  nor  that  of  the  widely  flared  nozzle  shown 
in  Fig.  17. 

If  the  tube  is  cylindrical  the  weight  of  steam  flowing  per 
second  reduces  with  -an  increase  in  length ;  at  75  pounds  the 
flow  through  a  j£"  tube  was, 

}&'f  long  900  Ibs.  per  hour. 

i/x  long  892  Ibs.  per  hour. 

i^"  long  864  Ibs.  per  hour. 

To  determine  the  weight  of  steam  passing  through  an 
orifice,  it  is  often  convenient  to  use  a  simple  formula  instead 
of  resorting  to  actual  measurement.  The  following  equation 
was  found  by  R.  D.  Napier  to  give  results  very  close  to 
actual  weighings,  with  results  only  about  2  per  cent,  low  at 
70  pounds,  and  i  per  cent,  low  at  120  pounds;  Rankine  has 
also  recommended  it  for  approximate  calculations.  The 
formula  is 

PX  A 
w=-^~ <S) 

where 

A  =  area  of  the  orifice  in  square  inches, 

P  =  absolute  pressure,  =  gauge  pressure  plus  15, 

w  =.  weight,  of  steam  discharged  in  pounds  per  second. 

Knowing  the  weight  of  a  cubic  foot  of  steam  at  the  pres- 
sure in  the  orifice,  the  velocity  of  the  jet  at  that  point  can 


62  THE   GIFFARD  INJECTOR. 

easily  be  found.  It  is  better,  however,  to  apply  the  simple 
approximate  formula  given  by  Rankine,  which  is  based 
upon  the  energy  exerted  by  the  steam  during  expansion  : 

V—  V  2g  v  ==  8.025  v/77  ...........  (10) 

--      +  -2     (1105590-  -5  10.2  7-0.   .  (ii) 


Here  V  is  the  velocity  in  feet  per  second  at  the  lower 
pressure  where  the  absolute  temperature  is  Tt  =  /  -f  461.2  ; 
and  7J  the  absolute  initial,  which  at  120  pounds  steam  is 
T!  =  350.03  4-  461.2  =  811.23  degrees;  the  pressure  being 
known,  the  actual  temperature  of  the  steam  can  be  obtained 
from  any  steam  table,  and  the  absolute  temperature,  by 
adding  461.2.  The  use  of  this  formula  is  to  calculate  the 
velocity  of  the  jet  at  the  instant  the  particles  of  steam  strike 
the  water  and  the  transfer  of  momentum  is  effected  ;  this 
one  is  the  simplest  to  apply,  as  it  is  not  complicated  by  other 
calculations. 

The  application  of  this  formula  for  finding  the  velocity 
requires  the  assumption  that  the  work  performed  by  steam 
during  discharge  is  equal  to  that  exerted  against  a  piston 
moving  in  a  cylinder,  and  that  no  heat  is  received  from,  or 
given  out  to,  external  bodies  ;  in  other  words,  the  relation 
between  pressure  and  volume  in  all  parts  of  the  jet  follows 
the  law  of  adiabatic  expansion.  During  this  process,  a  cer- 
tain percentage  of  steam  is  condensed,  which  increases  with 
the  difference  between  the  initial  and  terminal  pressures  ; 
for  example,  in  expanding  from  120  pounds  to  the  atmos- 
phere, 12^5-  per  cent,  of  the  weight  discharged  is  condensed, 
leaving  8yT6^  per  cent,  of  gaseous  steam  ;  when  the  final 
pressure  is  —  22"  vacuum,  as  in  the  case  of  the  injector  quoted 
on  page  58,  i  pound  of  steam  at  the  moment  of  impact  will 
contain  0.179  pound  water  and  0.821  pound  steam. 

These  values  may  be  calculated  for  any  degree  of  expan- 
sion by  means  of  formula  (12)  : 


THE  STEAM  NOZZLE.  63 

where  xl  and  x2  are  the  weights  of  steam  at  the  absolute 
initial  and  terminal  pressures.    (If  initial  steam  dry,  xl  =  i.) 
TI  and  7^2,  =  absolute  temperatures  =  (t  +  461.2), 
TI  and  r2,  =  latent  heat  under  the  two  conditions, 
0l  and  ft,,  =  entropy  of  liquid. 

These  terms  can  be  obtained  from  Steam  Tables ;  the 
values  of  0  most  frequently  used  are,  however,  given  in 
Table  III,  page  66. 

Formula  (No.  12)  will  be  found  of  use  in  calculating 
results  from  experimental  data,  and  for  supplying  the  value 
of  x^  in  (13),  by  which  the  velocity  of  the  jet  can  be  con- 
veniently found : 


F=  8.025  \/  778  (*i  n  +  ft  —  **rt  —  ft)  ........  (13) 

and  the  weight  discharged, 

_  ____  A^V^  ____ 

"144  (x.t  (5—o.oi6)  +  0.016)*  ' 
where 

V  —  velocity. 

w  =  weight  discharged,  in  pounds  per  second. 

A  =  area  of  the  nozzle  at  smallest  section,  in  square  inches. 

ft  and  q.2  =  heat  of  the  liquid  at  the  terminal  pressures. 

5  =  volume  i  pound  steam  in  cubic  feet,  at  final  pressure. 

By  way  of  illustrating  the  use  of  these  formulae,  the  velocity 
of  a  jet  of  steam  discharging  from  a  reservoir  at  120  pounds 
pressure  into  the  air  will  be  calculated.  The  steam  will  be 
supposed  to  be  dry,  and  to  follow  the  law  of  adiabatic  ex- 
pansion. The  value  of  xt  must  be  first  determined  by  (12). 
As  the  steam  is  supposed  to  be  dry  in  its  initial  state,  xl  = 
i  ;  the  other  terms  are  as  follows  : 

6l  =  0.5027  rj  =  867.3  7\  =  350.3  -f  461.2  =  8  1  1.5  ql  =  321.4 
03=r  0.3135  r2  =  966.07  T2  =  2i2  +461.2  —  673.2  ?2 

,   867.3 
0.5027  —  0.3135  +  x-  -- 

~5  =  0.876 


673.2 


V=  8.025  \/  778  (867.3  +  32I-4—  0.876  x  966.07  —  180.5)  =  2848.2 
Formula  (10)  gives  2827  feet  per  second,  which  agrees 
fairly  well  with  this  result. 


OF  THB 


64  THE  GIFFARD  INJECTOR. 

If  dry  steam  at  the  same  pressure  expand  to  — 22" 
vacuum,  or  4  pounds  absolute,  the  value  of  x^  will  be  found 
to  be  0.8243,  and  the  final  velocity,  3446  feet,  or  ^3  mile  per 
second;  calculated  by  (10),  V  is  3443  feet. 

The  presence  of  water  in  the  steam  is  shown  by  the  change 
in  the  appearance  of  a  jet  discharging  into  the  air ;  the 
clear  bluish  portion  of  the  jet  adjoining  the  orifice  becomes 
an  opaque  white.  The  effect  upon  the  velocity  can  be  found 
by  giving  a  lower  value  than  unity  to  jqin  formula  (12).  If 
5  per  cent,  of  water  is  entrained,  xl  =  0.95,  and  in  the  pre- 
vious example  x2  becomes  0.7899,  and  the  final  velocity  is 
3223  instead  of  3446  feet. 

Besides  retarding  the  velocity,  entrained  water  has  an  in- 
jurious effect  upon  the  surfaces  of  the  tubes,  cutting  and 
abrading  the  metal  wherever  soft  spots  occur;  dry  pipes 
should  be  used  to  prevent  this  trouble  and  all  pockets  or  de- 
pressions in  the  steam  pipe  avoided;  for  prompt  starting, 
efficient  action,  and  general  reliability  of  an  injector  are  much 
enhanced  by  attention  to  this  apparently  trivial  condition. 

The  area  of  the  steam  nozzle,  upon  which  depends  the 
weight  of  steam  used  per  hour,  can  best  be  defined  in  terms 
of  the  area  of  the  delivery  tube.  This  varies  with  the  pat- 
tern of  the  injector,  and  the  purpose  for  which  the  instrument 
is  designed.  From  superficial  considerations,  it  would  appear 
that  if  this  ratio  were  made  unity, — z.  e.,  the  steam  nozzle 
area  =  delivery  tube  area, — the  jet  would  just  have  sufficient 
power  to  sustain  the  initial  pressure ;  the  nearest  approach 
to  this  in  experimental  work  is  with  the  ratio  1.007  to  i-ooo, 
but  in  actual  practice,  on  account  of  tlje  necessity  of  a 
margin  of -counter  pressure,  the  ratio  varies  from  2  to  i,  to 
3  to  i ;  in  the  exhaust  injector  this  is  increased  to  1 6  to  i,  as 
the  ratio  of  the  initial  to  the  terminal  pressure  is  i  to  6,  or 
1 6  pounds  to  96  (absolute). 

The  motive  element  in  the  injector  is  the  steam  supply, 
and  the  work  performed  is  raising  the  water  to  the  level  of 
the  instrument  and  delivering  it  against  the  pressure  of  the 
boiler.  From  the  stand  point  of  mechanical  efficiency,  it  is 
obvious  that  the  smaller  the  weight  of  steam  required  to 


THE  STEAM  NOZZLE.  65 

perform  this  work,  the  more  economical  will  be  the  opera- 
tion. The  condensation  of  the  motive  jet  is  the  source  of 
economy  in  this  method  of  feeding,  as  the  only  loss  is  the 
small  amount  heat  radiated.  The  employment  of  a  larger 
quantity  of  steam  than  is  absolutely  necessary,  would  be 
using  the  instrument  as  a  heater,  or  similar  to  the  applica- 
tion of  a  jet  of  steam  to  the  suction  pipe  of  a  pump  for  the 
purpose  of  warming  the  water. 

The  raising  of  the  temperature  of  the  feed  water  is  bene- 
ficial, but  can  best  be  accomplished  by  other  means;  by 
utilizing  the  heat  of  the  waste  products  in  the  smoke-box 
or  stack,  or  by  using  the  heating  surface  of  the  boiler  itself, 
instead  of  absorbing  available  energy  from  the  boiler  for  the 
purpose  of  performing  subordinate  work.  This  is  specially 
applicable  to  service  on  locomotives,  where  the  high  rate  of 
speed  employed  at  the  present  time  necessitates  the  strictest 
economies  in  the  use  of  steam,  and  the  application  of  the  full 
capacity  of  the  boiler  to  its  primary  use,  supplying  steam  to 
the  cylinders ;  it  frequently  happens  that  the  injector  can  only 
be  placed  in  operation  when  the  excessive  strain  is  relieved  by 
a  stop  at  a  station  or  during  a  run  on  a  down  grade.  On 
the  other  hand,  the  most  economical  results  are  obtained, 
not  by  an  intermittent  water  supply,  but  by  maintaining  a 
constant  water  level  and  a  continuous  feed. 

The  actual  amount  of  steam  required  during  the  feeding 
of  a  locomotive  boiler  is  not  generally  realized ;  an  evapora- 
tion of  2,500  gallons  of  water  per  hour,  requires,  with  some 
patterns  of  injectors,  2,300  Ibs.  of  steam,  which,  at  an  esti- 
mated rate  of  35  Ibs.  per  H.  P.,  amounts  to  65  H.  P.  If  the 
steam  were  used  to  best  advantage,  this  could  be  reduced  to 
about  45  H.  P. ,  and  the  temperature  of  the  water  entering 
the  boiler  would  be  lowered  approximately  25°.  It  is  of 
course  advantageous  to  supply  the  boiler  with  water  as  hot 
as  possible,  to  avoid  shrinkage  and  unequal  expansion  of- 
the  sheets ;  but,  as  can  be  easily  seen,  the  benefits  gained  in 
that  direction  by  raising  the  temperature  of  the  feed  by 
means  of  a  jet  of  high  pressure  steam,  seldom  compensate 
for  the  loss  of  available  steam  supply. 
5 


66 


THE  GIFFARD  INJECTOR. 


There  can  be  no  question  but  that  the  injector  is  superior 
to  all  other  devices  for  feeding  locomotive  boilers  that  have 
yet  been  introduced,  but  its  action  should  be  as  efficient  as 
possible,  in  order  that  the  steam  and  fuel  consumption 
which  may  properly  be  charged  to  its  account,  can  be  re- 
duced to  the  minimum. 

A  short  table  giving  the  value  of  6  may  be  found  to  be 
convenient  when  complete  tables  are  not  at  hand : 

TABLE  III. 


Absolute 
pressure, 
Ibs.  persq.in. 

6 

Absolute 
pressure, 
Ibs  persq.  in. 

e 

Absolute 
pressure, 
Ibs.  persq.in. 

6 

Absolute 
pressure, 
Ibs.  per  sq.  in. 

e 

Absolute 
pressure, 
Ibs.  persq.  in. 

0 

Absolute 
pressure, 
Ibs.  persq.  in. 

0 

I. 

.1329 

6 

.2480 

14.7 

•3135 

40 

.3921 

65 

•4337 

QO 

4633 

2 

•1754 

7 

.2587 

2O 

•3363 

45 

.4020 

70 

.4402 

IOO 

•4733 

3 

.2013 

8 

.2682 

25 

•3539 

50 

.4109 

75 

.4464 

120 

.49" 

4 

.2203 

10 

.2842 

30 

.3685 

55 

.419! 

80 

.4522 

ISO 

•5133 

5 

•2353 

12 

.2976 

35 

.3811 

60 

.4267 

85 

•4579 

2OO 

.5429 

An  efficiency  comparison  of  different  styles  of  injectors 
can  be  made  either  by  rating  the  delivery  of  the  injector  in 
cubic  feet  or  pounds  per  hour  in  terms  of  the  area  of  steam 
nozzle,  or  by  determining  the  ratio  of  the  weight  of  steam 
used  to  the  weight  of  water  forced  into  the  boiler.  In  this 
connection  may  be  given  the  following  tests  of  some  of  the 
best-known  patterns  of  locomotive  injectors,  all  made  under 
precisely  the  same  conditions :  steam  120  pounds,  feed  tem- 
perature 65°  Fahr.,  height  of  lift  18".  Steam  dry. 


Name  of  Injector. 


Nominal  Size. 


Belfield No.  10 

Garfield No.    7 

Little  Giant No.  7 

Mack No.  7 

Metropolitan No.  9 

Monitor No.  9 

Sellers'  1887 No.  8% 


Weight  of  Water 

Delivered  per  Ib. 

of  Steam. 

9.69  pounds 

13-53 
12.92 

13-79 
13.16 
11.31 
13.80 


CHAPTER    VII. 

THE  ACTION  OF  THE  INJECTOR. 

NOTWITHSTANDING  the  fact  that  much  has  been  written 
upon  this  subject,  the  action  of  the  injector  still  appears 
mysterious  to  many  of  those  who  are  familiar  with  its  opera- 
tions. It  is  strange  that  the  reason  for  its  working  is  not  more 
generally  understood,  even  by  those  accustomed  to  operate 
it  daily,  especially  as  this  method  of  feeding  is  now  so  uni- 
versally employed  for  locomotive  and  stationary  boilers. 

The  simplest  method  of  considering  the  theory  of  the 
injector  is  to  eliminate  the  more  complicated  sides  of  the 
question  and  consider  it  solely  from  a  mechanical  point  of 
view ;  simply  as  an  apparatus  in  which  the  momentum  of  a 
jet  of  steam  is  transferred  to  a  more  slowly-moving  body  of 
water,  producing  a  resultant  velocity  sufficient  to  overcome 
the  pressure  of  the  boiler. 

The  high  velocity  attained  by  a  jet  of  steam  has  been  cal- 
culated, and  diagrams  have  been  given  that  show  the  fall  of 
pressure  and  increase  in  velocity  as  the  volume  is  increased 
according  to  the  laws  under  which  the  steam  expands. 
Suppose  that  a  nozzle  connected  with  a  reservoir  containing 
steam  at  120  Ibs.  pressure  discharges  i  Ib.  of  steam  per 
second ;  at  its  minimum  diameter,  the  steam  will  have 
reached  a  velocity  of  1407  feet,  but  when  the  terminal  pres- 
sure is  22"  vacuum,  the  velocity  will  be  3446  feet  per  second. 
I/et  us  suppose  that  this  jet  flows  into  a  combining  tube, 
which. is  able,  by  means  Of  the  great  conductivity  of  its 
walls,  to  abstract  sufficient  heat  to  completely  condense  the 
steam  at  a  final  pressure  of  22",  or  4  Ibs.  absolute.  This 
reduces  the  steam  to  a  solid  jet  of  water  having  a  cross 

67 


68  THE  GIFFARD  INJECTOR. 

section  T^¥  the  area  of  the  steam  while  passing  through  the 
steam  nozzle,  and  yet  does  not  in  any  way  affect  the  velocity, 
as  the  contraction  of  the  jet  is  entirely  lateral.  A  jet  of 
water  issuing  from  the  delivery  tube,  forced  out  by  the  pres- 
sure of  the  boiler,  would  have  a  velocity  nearly  equal  to 
that  due  to  the  head,  or  approximately,  133  feet  per  second, 
only  ^  of  that  of  the  jet  of  condensed  steam ;  but  an  injec- 
tor is  required  to  perform  useful  work,  forcing  a  supply  of 
feed  water  into  the  boiler ;  therefore  a  certain  weight  of  feed- 
water  must  be  added  which  will  take  the  place  of  the  cold 
walls  df  the  tube  for  the  purpose  of  condensation.  This 
mass  of  water  receives  the  energy  of  the  moving  steam, 
condenses  it,  and  the  two  fluids  move  along  together  through 
the  delivery  tube  with  a  terminal  velocity  greater  than  a  jet 
of  the  same  density  issuing  from  the  boiler.  If  the  weight 
pf  water  supplied  is  too  great,  the  steam  will  not  have  power 
enough  to  give  the  required  velocity  of  133  feet;  if  there  is 
an  insufficient  supply,  the  volume  of  the  steam  will  not  be 
reduced  sufficiently  to  pass  through  the  tubes,  and  in  neither 
case  will  the  injector  work  properly. 

Turning  again  to  figures,  and  taking  the  simplest  possible 
case,  we  can  follow  the  steam  through  its  whole  course 
within  the  tubes,  and  determine  the  relation  of  the  different 
parts  of  the  injector.  As  the  velocity  and  volume  of  the 
steam  at  the  instant  of  passing  the  minimum  diameter  of 
the  steam  nozzle  are  1407  feet,  and  5.05  cubic  feet,  respec- 
tively, and  after  complete  expansion  in  the  combining  tube 
3446  feet  (see  page  64)  and  74.2,  the  cross  section  of  the 
steam  jet  at  that  time  must  be, 

z-  X         —  =  5-99  times  the  area  of  the  steam  nozzle. 

3446          5-05 

During  complete  condensation,  the  volume  of  i  Ib.  of  steam 
shrinks  from  74.2  cubic  feet  to  o.  16  cubic  feet,  so  that  the 
cross  section  of  the  jet  after  condensation  is 

— X  — -       = the  area  of  the  steam  nozzle, 

74.2  i  774 

so  that  the  jet  of  condensed  steam  would  pass  through  an 


THE  ACTION  OF  THE  INJECTOR.  69 

orifice  yf*  the  area  of  the  steam  nozzle  at  a  velocity  of  3446 
feet  per  second. 

The  substitution  of  a  cone  of  water  as  the  condensing 
medium,  at  a  ratio  of  13  pounds  of  water  to  the  pound  of 
steam  —  as  this  is  a  fair  performance  of  a  locomotive  in- 
jector at  this  pressure  —will  increase  the  volume  of  the  jet 
(13  +  i)  =  14  times,  and  require  the  area  of  the  delivery 
tube  to  be  enlarged  to  7VV  Further,  the  addition  of  this 
weight  of  water  will  retard  the  motion  of  the  jet,  and  de- 
mands a  still  larger  orifice  of  entrance  ;  it  will  therefore  be 
necessary  to  determine  the  final  velocity  of  the  mixture 
before  the  size  of  the  delivery  tube  can  be  obtained.  The 
transfer  of  the  energy  of  the  steam  to  the  water  is  similar  to 
that  occurring  during  the  impact  of  two  inelastic  bodies, 
and  owing  to  the  fact  that  the  particles  of  steam  do  not  all 
strike  the  molecules  of  water  in  the  proper  direction,  and 
owing  to  the  obliquity  of  the  entrance  of  the  feed  into  the 
combining  tube,  and  also  other  causes,  a  loss  occurs  which 
varies  somewhat  under  different  conditions,  but  under  those 
assumed,  amounts  to  40  per  cent.  Multiplying  the  weight 
of  the  water  by  its  entrance  velocity  of  40  feet  due  to  the 
22"  vacuum  in  the  combining  tube,  and  adding  the  momen- 
tum of  i  Ib.  of  steam  at  a  velocity  of  3446  feet,  we  have  the 
following  equation  of  momentum,  which  determines  the 
velocity  of  the  mixture  : 

(i.oo  —  0.40)  x  (4°  X  13  -}-  3446  x  i)  =  14  X  v 
v  =  169.97  feet  per  second. 

The  temperature  of  this  mixture  would  probably  be  about 
150°,  and  i  Ib.  per  square  inch,  from  Table  II,  would  be 

equal  to  a  head  of  2.355  feet>  and  from  h  =  --,  and  h  =  p 
X  2.355  we  have 


. 

t>  —  —         —  -  —  =  --  ,  —  -  =  190.5  pounds  back  pressure 
2-355  X  64.4        151.66 

corresponding  to  this  velocity  ;  but  from  this  must  be  sub- 
tracted the  pressure  in  the  combining  tube  below  the  atmos- 


70  THE  GIFFARD  INJECTOR. 

phere,  2-2"  or  1 1  Ibs. ,  so  that  the  available  counter  pressure 
as  shown  on  the  gauge  will  be  179.5  Ibs. 

The  velocity  of  the  original  jet  is  now  reduced  from  3446 
feet,  as  in  the  assumed  case  when  passing  through  the  de- 
livery tube,  to  169.97  feet,  requiring  a  further  enlargement  of 
the  area,  in  order  that  the  augmented  volume  of  the  jet  may 
find  entrance  at  this  reduced  velocity.  Summing  up  the 
two  changes,  one  due  to  the  decrease  in  velocity,  and  the 
other  due  to  increase  of  volume,  we  have, 

-—  —  X  — —  = :  the  area  of  the  steam  nozzle ; 

169.97          774  2.72 

or,  in  other  words,  if  the  area  of  the  delivery  tube  be  taken 
as  unity,  the  area  of  the  steam  orifice  will  be  2.72,  and  the 
ratio  of  the  diameters  will  be  i  to  1.65,  which  approaches 
closely  the  proportions  in  ordinary  practice. 

It  is  thus  seen  that  the  whole  action  of  the  injector  de- 
pends upon  the  fact  that  the  velocity  of  a  jet  of  steam  dis- 
charging into  the  combining  tube,  is  20  to  25  times  that  of  a 
jet  of  water  issuing  from  a  boiler  under  the  same  pressure, 
and  that  the  enormous  reduction  of  the  volume  during  con- 
densation concentrates  the  momentum  of  the  jet  upon  an 
area  which  is  but  a  small  fractional  part  of  the  orifice  from 
which  it  issues,  leaving  a  large  margin  of  available  energy 
which  may  be  applied  to  useful  purposes.  As  condensation 
plays  such  an  important  part  in  the  operation,  it  is  seen  that 
any  condensible  gas  may  be  substituted  for  the  motive  steam, 
if  the  inherent  conditions  are  properly  considered,  but  some 
modifications  of  the  proportions  of  the  parts  as  used  in  the 
steam  injector  might  be  found  necessary  in  order  to  work 
satisfactorily  under  the  new  conditions. 

The  principle  of  the  action  of  the  injector  working  at  120 
pounds  steam  into  a  boiler  carrying  the  same  pressure,  may 
appear  more  easy  of  explanation  than  the  case  of  an  exhaust 
injector  forcing  water  into  a  boiler  at  80  pounds  steam  ;  that 
there  is  no  difference  beyond  a  change  in  the  proportions  of 
the  parts,  can  be  seen  from  the  following  example,  which 
will  be  worked  out  according  to  the  same  analysis  that  was 
applied  to  the  case  of  high  pressure  steam. 


THE  ACTION  OF  THE  INJECTOR.  71 

Assume  the  steam  at  o  (gauge),  or  14.7  pounds  absolute 
pressure,  containing,  as  it  arrives  direct  from  the  cylinder, 
about  10  per  cent,  of  moisture.  From  page  49  the  vacuum 
in  the  combining  tube  will  be  assumed  to  be  24"  or  3  pounds 
ab.  From  equation  (12),  we  find  that  i  pound  of  steam  in  its 
final  condition  will  contain  0.832  pound  of  steam,  and  o.  168 
pound  of  water  ;  its  velocity  after  complete  expansion  will 
be  found  from  (13), 


K=8.o25  \778  (0.90x966.07  -f-  181.6—0.832x1015.3—109.8)  =  2205  ft. 

To  work  against  a  pressure  of  80  pounds,  the  delivered 
water  must  be  forced  out  of  the  combining  tube,  in  which 
the  pressure  is  12.7  pounds  below  the  atmosphere,  so  that 
the  total  pressure  against  which  the  jet  must  be  capable  of 
working  is  80  -f  12.7  =  92.7  pounds  ;  this  requires  a  terminal 
velocity  of  1  35  feet,  under  the  assumption  that  the  steam  is 
all  condensed  and  that  its  density  is  unity.  The  feed  water 
enters  under  a  head  of  6  feet,  and  with  a  velocity  corres- 
ponding to  the  sum  of  the  partial  vacuum  and  the  head, 
approximately  48  feet  per  second.  A  somewhat  greater 
percentage  of  loss  must  be  taken  than  in  the  other  case,  as 
the  action  of  the  jet  is  not  as  efficient,  and  it  does  not  seem 
as  if  it  could  be  made  so  ;  taking  0.50  as  the  value  of  this 
coefficient,  we  have  for  the  equation  of  momentum,  from 
which  the  weight  of  feed  water  may  be  obtained, 

(i  X  2205  +  48  x  W)  xo.5o=(JF+i)  x  135, 
whence 

W-=  8.74  pounds  of  water  per  pound  of  steam, 

which  corresponds  to  the  usual  practice. 

In  both  the  examples  given  the  simplest  conditions  were 
assumed  and  all  uncertain  elements  avoided.  The  jet  as  it 
passed  through  the  delivery  tube  was  supposed  to  have  the 
same  density  as  water  at  the  same  temperature  ;  in  fact,  this 
seldom  occurs,  as  there  is  almost  always  a  part  of  the  steam 
uncondensed  until  the  mixture  has  passed  far  into  the  deliv- 
ery tube,  and  there  is,  in  addition,  a  volume  of  air  mixed 
with  the  steam  that  displaces  a  corresponding  volume  of 
water  and  gives  to  the  jet  its  white,  opaque  appearance. 


72 


THE  GIFFARD  INJECTOR. 


This  quantity  of  air  will  depend  upon  the  manner  in  which 
the  boiler  is  fed,  and  the  condition  of  the  suction  pipes  and 
valves  and  stuffing-boxes  of  the  injector  or  pump,  as  the 
total  amount  of  air  contained  in  the  steam  is  greater  than 
can  be  held  in  solution  by  the  feed  water.  Experiments 
made  with  an  injector  placed  entirely-  under  water,  so  as  to 
collect  all  the  air  discharged  with  the  delivery,  showed  that 
this  amount,  though  very  variable,  was  by  no  means  inap- 
preciable;  a  No.  8  injector  at  120  pounds,  discharged  5.51 
cubic  feet  of  air  per  hour,  and  at  60  pounds,  4.38  cubic  feet, 
measured  at  atmospheric  pressure.  These  results  do  not 
represent  the  maximum  quantity,  but  the  mean  of  several 
tests. 

The  density,  however,  depends  chiefly  upon  the  percent- 
age of  steam  condensed,  and  is,  therefore,  intimately  con- 
nected with  the  water  ratio.  The  following  table  shows  the 
variation,  and  the  increase  in  the  velocity  of  the  jet  as  the 
density  decreases  :  steam  pressure,  135  pounds  absolute. 

TABLE  IV. 


tl 

V   U 

c 

fi'   ^ 

1SS 

3  gT 

c 

P.  60 

"2  a. 

2-S  P. 

en  {jj« 

g«« 

^>o 

h 

&S-S 

Ifcl 

O  ^fc    . 

P 

.52  a>  u 

•-i  3  3 

si 

rt-JJ 

& 

If 

«S 

•**  •*"*  " 

»2?  ^  W-t 

O  .*_»  cd  H 

**  ^5  8  w 

«0° 

5  •* 

c 

<C  M 

§ 

£ 

"S   C8   P«U5 

^ 

o  oft 

5 

p 

Q 

! 

4 

JF 

^7 

p 

P 

p 

A 

A- 

*) 

154° 

I2.OO 

3435- 

1653 

1  80. 

186.1 

0.788 

o.55i 

6>) 

167° 

10.33 

335«. 

1740 

199. 

236.4 

0.542 

0.524 

c] 

185° 

8.63 

3228. 

181.6 

215. 

302.8 

0.360 

0.493 

d] 

209° 

7.02 

3058. 

177-3 

202. 

346.3 

0.261 

0.432 

e] 

240° 

5.60 

2970. 

147-2 

H3- 

294.0 

0.250 

0.310 

f) 

268° 

4.69 

2890. 

141.6 

130. 

305.0 

0.2  1  1 

0.265 

The  ratio  of  water  to  steam  that  produces  the  highest 
back  pressure  is  shown  in  experiment  (c}  as  the  energy  of 
the  jet  is  then  at  its  maximum ;  with  less  water,  the 
density  of  the  jet  is  too  low,  even  though  the  velocity  is 
greater,  and  below  that  ratio  the  density  rises,  but  the 


THE  ACTION  OF  THE  INJECTOR.  73 

velocity  is  insufficient,  on  account  of  the  large  increase  in 
the  weight  of  the  mixture. 

Simple  formulae  can  be  applied  to  find  the  density  :  if  the 
back  pressure  is  known,  find  the  velocity  of  a  jet  of  water 
at  the  temperature  of  delivery,  which  designate  by  v,  and 
the  actual  velocity  by  v^.  Let  A  be  the  density,  and  H  the 
back  pressure  expressed  in  feet. 

Then 


If.  A  =  the  area  of  the  delivery  tube,  the  theoretical  capa- 
city =  v  x  A,  and  we  obtain  the  following,  by  substituting 
(15)  and  reducing 

62.4  A  v^  A  _        Weight  of  actual  jet       _  Actual  capacity  _ 

A  v~     Weight  of  jet  unit  density      Theoret.  capac-         ^ 


so  that 

A  =  (  __  Actualcapadty      \*  _  (i6) 

V  Theoretical  capacity/ 

The  actual  velocity  in  the  table  was  found  by  dividing  the 
calculated  velocity  by  the  square  root  of  the  density,  and 
the  changes  in  the  velocity  of  the  entering  water  and  the 
discharging  steam  are  due  to  the  variation  of  the  pressure 
within  the  combining  tube  with  the  temperature  of  the 
delivery. 

Experiments  (  e  )  and  (/")  were  made  with  the  overflow 
closed,  permitting  a  high  pressure  in  the  confined  overflow 
chamber,  otherwise  there  would  have  been  a  discharge  of 
steam  ;  but  in  many  cases  where  two  or  more  apertures  in 
the  combining  tube  are  contained  in  the  same  chamber  and 
only  closed  to  admission  of  air  by  a  light  check  valve,  the 
delivery  temperature  may  rise  above  the  boiling  point  of 
water  at  atmospheric  pressure.  In  one  pattern  of  injector, 
where  several  overflows  are  connected,  the  author  has  seen 
the  temperature  of  the  water  going  to  the  boiler  carrying 
140  pounds  of  steam,  reach  250°  Fahr.,  with  the  overflow 
chamber  closed  only  by  a  light  check  valve  weighing  but  a 
few  ounces. 


74  THE  GIFFARD  INJECTOR. 

As  the  proportion  of  water  to  steam  is  reduced,  and  the 
density  of  the  jet  diminished,  it  will  be  noticed  that  the 
value  of  the  coefficient,  as  given  in  the  last  column,  also 
grows  less ;  when  the  water  ratio  was  i  to  13,  as  taken  in 
the  example  at  the  opening  of  this  chapter,  this  value  was 
taken  at  0.60,  but  when  the  weight  of  water  per  pound  of 
steam  is  7.02,  this  coefficient  falls  to  0.432. 

The  actual  causes  of  the  loss  covered  by  this  term  cannot 
be  definitely  described ;  it  is  very  probable  that  the  whole 
mass  of  steam  is  not  entirely  condensed  at  the  instant  of 
impact,  and  there  remains  a  certain  amount  of  elasticity 
that  produces  a  rebound  and  an  interference  with  the  motion 
of  the  particles  of  steam  following.  A  jet  of  steam  dis- 
charging into  a  pail  of  water  will  blow  the  water  in  all 
directions,  and  only  a  small  portion  of  the  steam  will  be 
condensed ;  the  warmer  the  water,  the  greater  this  ten- 
dency, so  that  it  is  not  at  all  surprising  that  with  high  tem- 
peratures of  delivery,  due  either  to  warm  feed  water  or 
insufficient  feed  supply,  the  coefficient  of  efficiency  should 
have  a  lower  value  than  when  the  conditions  of  working  are 
more  nearly  normal.  The  oblique  angle  at  which  the  water 
enters  the  combining  tube  is  also  disadvantageous,  while  the 
roughened  surfaces  of  the  tubes  add  their  quota  to  the  gen- 
eral sum  of  losses,  which  will  be  represented  by  the  coeffi- 
cient K. 

It  is  exceedingly  difficult,  in  fact  almost  impossible,  to 
represent  algebraically  the  conditions  that  obtain  within  the 
combining  tube  of  an  injector,  and  to  frame  an  equation 
that  will  apply  to  all  conditions  or  all  types  of  instruments. 
The  shape  of  the  tubes,  the  conditions  of  the  surfaces,  and 
the  proportions  of  the  orifices,  all  introduce  special  consid- 
erations that  would  so  complicate  an  equation  as  to  invali- 
date its  utility ;  fundamental  relations  can,  however,  be 
shown  to  exist,  and  simple  equations  given  to  prove  the 
mechanical  theory  as  already  outlined  ;  these  will  be  fol- 
lowed by  formulae  based  upon  the  heat  theory. 

Taking  the  most  elementary  form  of  injector,  one  with  a 
single  set  of  tubes  and  but  one  overflow  in  the  combining 


THE  ACTION  OF  THE  INJECTOR.  75 

tube,  assume  i  pound  of  steam  per  second  from  the  steam 
nozzle  as  the  actuating  force.  This  steam  will  have  a 
velocity  V  due  to  the  work  performed  in  expanding  from 
the  initial  pressure  of  the  boiler  to  the  low  pressure  in  the 
combining  tube.  Its  momentum  will  therefore  be 

7  ..............  "» 

The  feed  water  enters  with  a  velocity  v2  due  to  the  differ- 
ence between  its  head  h  and  the  absolute  pressure  within  the 
combining  tube  ;  as  these  pressures  must  be  reckoned  above 
a  perfect  vacuum,  the  pressure  in  the  tube  becomes  (34  —  ^), 
and  if  the  water  comes  to  the  injector  under  a  head  h,  the 
total  head  forcing  it  into  the  combining  tube  is  (34  —  h^  -f  h). 
Calling  the  weight  of  water  W,  the  momentum  of  the  en- 
tering water  is 

w  v,  =  ^v/277^v+Tj 
g  g 

The  sum  of  these  two  equations  represent  the  momenta  of 
the  separate  masses  before  they  come  in  contact,  but  during 
impact  and  the  condensation  of  the  steam  jet,  there  is  a  loss 
of  momentum  due  to  causes  already  outlined  and  indicated 
by  the  coefficient  K.  The  sum  of  (17)  and  (18)  is  the  mo- 
mentum of  the  mass  as  it  approaches  the  delivery  tube  ;  its 
velocity  must  depend  upon  the  difference  between  the  abso- 
lute permissible  back  pressure  —  expressed  in  feet  —  and  the 
pressure  in  the  combining  tube,  or  (H  —  h^.  Therefore 


and  the  momentum  of  the  combined  mass  is, 

(y+o     _____ 

—j-     </2g(ff  —  hd  .........  (19) 

The  complete  equation  of  momentum  is 


76  THE  GIFFARD  INJECTOR. 

Solving  for  W^we  obtain  the  ratio  of  the  weight  of  water 
forced  into  the  boiler  per  pound  of  steam, 


(34- 

If  hv  is  not  known  and  cannot  be  readily  found,  it  may  be 
assumed  to  be  about  24"  vacuum  or  7.3  feet  absolute  pres- 
sure when  the  delivery  temperature  is  150°,  and  26",  or  4.7 
feet  absolute,  at   130°,  although  a  slight  variation  will  not 
materially  affect  the  results.     Upon  h  and  h±  depends  the 
velocity  of  entrance  of  the  water  into  the  combining  tube, 
and  these  terms  do  not  appear  in  their  true  importance  in 
the  equation,  as  the  area  of  entrance  is  not  expressed,  but  is 
assumed  to  be  of  the  most  advantageous  proportion  ;   this 
is  only  the  case  in  the  self-adjusting  or  adjustable  combining 
tube  form  of  injector,  shown  in  Figs,  i  and  2  or  3  ;  as  all  the 
water  must  enter  through  this  opening,  whose  area  we  will 
designate  by  B,  the  value  of  Win  the  ordinary  fixed-nozzle 
pattern  would  be 

^=62.39  B  v/  2g  (34  —  hi  -f  h)  .........  (22) 

If  the  supply  is  lifted,  h  must  be  negative  ;  if  the  feed  water 
flows,  h  is  positive.  To  show  the  change  in  the  value  of  W 
with  different  heights  of  lift  (  —  h  )  the  following  tests  of  a 
fixed-nozzle  injector,  adjusted  for  its  maximum  capacity  at 
i  foot  lift,  are  given  in  Table  V.  Steam  was  constant  at 
65  pounds  pressure,  and  the  area  of  the  water  entrance  to 
the  combining  tube  fixed  ;  feed  and  steam  valves  wide  open. 

TABLE  V. 


Ratio  Wt. 

Ratio  Wt. 

Lift  in 

Capacity  Cubic 

Water  to 

Lift  in 

Capacity  Cubic 

Water  to 

Feet. 

Feet. 

Steam. 

Feet. 

Feet. 

Steam. 

—  h 

Q 

W 

—  h 

Q 

W 

I 

1  08 

H54 

8 

87.8 

11.83 

2 

107.2 

H.43 

10 

8l.8 

II.  O2 

3 

104-9 

14.13 

12 

76.9 

9-92 

4 

101.9 

13.73 

14 

66.9 

8.97 

5 

97-9 

13.18 

16 

60.8 

8.13 

6 

94.8 

12.76 

18 

583 

7.72 

7 

90.4 

12-43 

20 

51-6 

6.89 

In  the  self-adjusting  injector,  the  area  B  changes  auto- 
matically with  the  steam  pressure,  so  that  an  increase  in  the 


THE  ACTION  OF  THE  INJECTOR.  77 

height  of  lift  affects  the  capacity  but  slightly.  A  well 
known  pattern  of  the  double-jet  type  at  60  pounds  steam, 
gave  the  following  capacities  at  different  lifts, 

4  Feet  Lift.  12  Feet  Lift.  24.  Feet  Lift. 

150.6  cubic  feet.       134.6  cubic  feet.          78.1  cubic  feet. 

In  both  (21)  and  (22)  the  head  of  water  representing  a 
perfect  vacuum  was  taken  as  34  feet;  this  corresponds 
closely  to  a  temperature  of  40°,  but  if  the  temperature  of  the 
feed  rises,  vapor  of  water  is  given  off  which  reduces  the 
vacuum  correspondingly.  The  following  table  gives  values 
that  may  be  substituted  for  34  in  the  above  equation  with 
different  temperatures  of  feed  water : 

TABLE  VI. 


Feed  Temp.  Vacuum  in  Feet. 

t\ 

4°  34 

70  33 

90  32.2 

ioo  31.4 

120  29.7 

130  27.3 


Feed  Temp.  Vacuum  in  Feet, 

'i 

140  25.9 

150  24.8 

160  22.5 

180  16.9 

200  9.3 

212  O.O 


The  chief  criticism  against  the  formula  denoting  the  in- 
terchange of  momenta,  is  that  there  is  no  term  in  the  equa- 
tion that  indicates  the  use  of  condensible  gases ;  as  written, 
air  or  any  other  permanent  gas  could  be  substituted  for 
steam  and  all  the  conditions  satisfied;  yet,  as  has  been 
shown,  the  principle  upon  which  the  injector  acts,  precludes 
the  use  of  all  gases  save  those  that  may  be  reduced  to  a  liquid 
form  under  the  conditions  that  obtain  within  the  combining 
tube  of  an  injector. 

The  co-efficient  K,  which  is  such  an  important  factor  in 
the  equation  of  momenta  (21),  seems  to  depend  somewhat 
on  /,  but  chiefly  upon  (/2  —  tj,  the  increase  in  the  tempera- 
ture of  the  feed  water.  As  the  heat  of  the  water  supplied 
rises,  the  weight  of  water  delivered  per  pound  of  steam  de- 
creases, and  the  coefficient  K  has  also  a  less  value  as  is 
shown  by  Table  VII ;  this  table  also  gives  the  capacity,  the 
value  of  W,  and  the  density  of  the  jet  at  120  pounds  steam, 
in  a  No.  8  Self-adjusting  Sellers'  injector,  placed  i  foot  above 
the  feed  level. 


78  THE  GIFFARD  INJECTOR. 

TABLE  VII. 


Feed 
Temp. 
t\ 

a)    65 
b)    80 

c]  H5 
d)  130 

Delivery 
Temp. 
k 

144-5 
160.0 
202.5 
226.0 

Water  to 
Steam. 
IV 

!3-53 
13.26 
11.63 
10.36 

Cubic  Feet 
per  Hour. 
Q 
278.7 
274.2 
239.2 
213.0 

Density 
of  Jet. 
A 

0.8836 
0.8154 
0.7490 
0.6430 

Coeffi- 
cient. 
K 

0-595 

0.583 
0.525 
0-473 

The  falling  off  of  the  capacity  with  the  increase  in  tlt  is 
caused  by  the  reduced  vacuum  within  the  combining  tube, 
and  the  change  in  the  terminal  velocity  of  the  steam  jet; 
this  could  be  partially  remedied  by  augmenting  h  in  (22)  as 
occurs  in  the  double  jet  pattern  of  injector,  but  yet  it  may  be 
stated  as  a  general  rule,  that  under  conditions  otherwise  the 
same,  the  lower  the  temperature  of  the  feed  water  supplied, 
the  greater  will  be  the  capacity.  In  the  case  of  the  double 
jet  type,  the  weight  of  water  passing  through  a  unit  section 
of  delivery  tube  is  never  as  great  as  in  a  single  jet  injector, 
because  the  warming  action  of  the  first  set,  reduces  the  rate 
of  condensation  within  the  forcing  combining  tube,  and 
lowers  the  density  of  jet. 

It  follows,  therefore,  that  in  order  to  give  the  same  capac- 
ity as  a  single  jet,  the  area  of  the  delivery  tube  -of  a  double- 
jet  injector  must  be  made  considerably  larger;  the  amount 
of  increase  required  depends  upon  the  proportions  of  the 
tubes,  and  may  be  anywhere  from  13  to  80  per  cent.  The 
action  of  the  first  set,  although  disadvantageous  as  far  as  the 
warming  of  the  water  is  concerned,  yet  produces  a  pressure 
at  the  entrance  to  the  combining  tube  of  the  forcing  set  that 
increases  its  power  of  taking  hot  water  ;  this  pressure  rises 
with  the  steam  pressure  and  also  with  the  temperature  of  the 
supply.  In  a  series  of  tests  made  with  an  injector  of  this 
type,  the  following  results  were  obtained, 


Pressure 
Steam.  between  Sets. 

40  Ibs.  2    Ibs. 

70  "  8.5  " 


Pressure 
Steam.  between  Sets. 

90  Ibs.  17  Ibs. 

120    "  27    " 


when  the  feed  temperature  was  63  degrees,  but  when  raised 
to  120  degrees  the  intermediate  pressure  was  22  Ibs,  at  90 
Ibs.  steam,  and  40  Ibs.  at  120  Ibs.  steam. 


THE  ACTION  OF  THE  INJECTOR.  79 

As  the  delivery  of  an  injector  depends  directly  upon  the 
velocity  of  the  jet  and  its  density  at  the  instant  of  passing 
the  smallest  diameter  of  the  delivery  tube,  it  follows  that  the 
capacity  will  be  proportional  to  the  square  root  of  the  terminal 
pressure  plus  a  constant  :  if  P  is  the  boiler  pressure  as  indi- 
cated by  gauge,  Q  the  capacity  in  cubic  feet  per  hour,  D  the 
diameter  of  the  delivery  tube  in  millimetres,  (i  millimetre 
=  0.0397")  —  as  many  manufacturers  use  the  French  system 
—  we  have,  approximately, 


Q  =  0.374  n*v  P  +  18  .......  •  •  .  .  .  (23) 

This  applies  to  self-adjusting  injectors  up  to  that  pressure  at 
which  the  maximum  capacity  commences  to  reduce,  but 
does  not  refer  to  the  double  jet  type,  although  a  fair  ap- 
proximation for  the  other  class. 

In  the  following  Table  is  given  the  weights  of  water  that 
should  be  delivered  per  pound  of  steam  by  a  well-designed 
injector  at  the  steam  pressures  ordinarily  used: 


TABLE  VIII. 


Gauge  Pressure.  W. 

10  Ibs.  33     Ibs. 

20     "  29.2    " 

40     "  23       " 

70     "  17.8    " 


Gauge  Pressure.  W. 

loo  Ibs.  15.0  Ibs. 

120     "  13.6    " 

150     "  12.6    " 

200      "  10.3     " 


Thus  far  the  mechanical  action  alone  has  been  discussed, 
but  as  the  heat  received  by  the  feed  water  during  the  process 
of  injection  is  one  of  the  chief  advantages  of  the  system  of 
feeding  upon  which  the  injector  is  based,  the  consideration 
of  the  thermal  action  will  now  be  taken  up. 

In  order  to  supply  the  energy  necessary  to  give  the  final 
velocity  to  the  particles  of  steam  during  expansion,  an 
amount  of  heat  must  be  absorbed  corresponding  to  the  work 
performed ;  according  to  the  theory  assumed  under  which 
expansion  takes  place,  all  the  heat  required  must  be  fur- 
nished by  the  steam  itself,  and  as  the  greater  part  of  the  heat 
contained  in  the  steam  is  latent,  a  portion  of  the  gas  must 
be  condensed  ;  so  that  in  its  final  state  the  steam  is  composed 
of  a  mixture  of  steam  and  water,  in  proportions  which  may 
be  determined  by  equation  (12).  After  expanding  to  the 


80  THE  GIFFARD  INJECTOR. 

pressure  within  the  combining  tube,  the  steam  strikes  against 
the  cold  water,  its  momentum  is  checked  and  its  energy  of 
motion  transformed  to  heat ;  this  is  at  once  absorbed  by  the 
feed,  as  is  also  the  remaining  sensible  and  latent  heat  in  the 
steam  mixture.  It  will  be  shown  that  all  the  energy  that  is 
apparently  wasted,  reappears  in  the  form  of  heat,  so  that 
the  injector  may  be  considered  as  a  theoretically  perfect  de- 
vice for  boiler  feeding  purposes,  and  its  thermal  efficiency  as 
unity ;  the  actual  number  of  heat  units  that  are  lost  by 
radiation  that  can  be  charged  directly  to  the  instrument 
itself  is  inappreciable  compared  with  those  contained  in  the 
delivered  water. 

Referring  again  to  figures,  take  an  injector  which  receives 
steam  at  120  pounds  and  feed  water  at  68°,  forcing  13  pounds 
of  water  per  pound  of  steam  against  a  permissible  counter- 
pressure  of  141  pounds,  at  a  delivery  temperature  of  150°, 
and  apply  the  analysis  of  the  transfer  of  heat  just  outlined. 

During  the  expansion  of  i  pound  of  steam  from  135  pounds 
to  4  pounds  (absolute)  there  is  an  amount  of  energy  de- 
veloped that  is  represented  by  U 'in  equation  (n)  or,  by  the 
term  under  the  radical,  in  (13).  Taking  the  latter  equation, 
and  substituting  the  figures  previously  used,  and  retaining 
the  result  in  heat  units, 

•*i  ri  +  4i  ~  •*"»  r>2  —  Q-2  —  237-07  Thermal  Units (24) 

The  water  flowing  into  the  combining  tube  possesses  a 
small  amount  of  energy  which  may  be  represented  by 

S  X  %  =  -W  (  34  +  k  ~  *'>  =iVto  +  -9-4) 
=0.75  Thermal  Units .  (25) 

where  33  is  the  head  of  water  in  feet  equal  to  the  vacuum,  h 
the  head  under  which  the  feed  flows  to  the  injector  and  has 
a  minus  sign  if  the  water  is  lifted ;  h^  the  absolute  pressure 
in  the  combining  tube  expressed  in  feet ;  v.2  is  the  velocity 
of  entrance;  /z,  —  i  foot. 

These  two  equations  represent  the  motive  power  in  the 
injector  expressed  in  thermal  units,  one  of  which  is  taken  as 
equal  to  778  foot  pounds  of  work.  This  energy  is  used  for 


THE  ACTION  OF  THE  INJECTOR.  81 

forcing  the  mixture  into  the  boiler  with  a  velocity  v,  which 

requires 

(i  +  W)      v>  __(!+  W) 
~T78"     *^-    ~7~78"  '*l) 

=  —  -^—  X  (  145  -  4  )  2.355  -  5-97  Thermal  Units  ....  (26) 

H  is  the  absolute  permissible  counter-pressure  in  feet  of 
head,  and  2.355  is  the  head  of  water  at  a  temperature  of 
150°  equal  to  i  pound  per  square  inch  from  Table  II.  This 
value  for  the  useful  work  performed  —  5.97  thermal  units  —  is 
very  small  compared  with  the  energy  expended  ;  adding  (24) 
and  (25)  and  subtracting  (26)  , 

(  237-  °7  4-  °-75  )  —  5-97  =  231.85  Thermal  Units. 

which  must  be  absorbed  by  the  feed  water.  The  increase  in 
temperature  is  therefore  231.85  -f-  13  =  17.83°  per  pound 
of  feed  water  due  to  the  loss  of  actual  energy  of  the  steam 
at  the  time  of  impact.  Expressed  algebraically 


which  represents  the  increase  in  the  temperature  of  the  de- 
livered water  due  to  the  absorption  of  the  remaining  energy 
of  the  steam  jet. 

When  intimate  contact  is  established  between  the  steam 
and  the  water,  condensation  is  effected,  and  the  latent  and 
sensible  heat  of  the  steam  transferred  to  the  feed.     At  this 
time,  the  heat  in  the  expanded  steam  is 

•*•«  r*  +  ft  +  32  —  t2    ...............  (28) 

an  equation  of  the  same  form  as  (24),  but  containing  the  final 
temperature  of  the  delivery,  as  the  temperature  of  the  steam 
mixture  cannot  fall  below  that  value.  (The  specific  heat 
of  water  between  32°  and  212°  is  so  nearly  constant,  that 
the  temperature  of  the  feed  is  substituted  for  the  '  '  heat  of 
the  liquid,"  as  the  change  simplifies  the  use  of  the  formula, 
and  the  difference  in  the  result  is  inappreciable.) 

From  (12)  and  also  from  the  calculations  made  on  page  64, 
we  find  the  weight  of  steam  remaining  in  i  pound  of  initially 
6 


82  THE   GIFFARD  INJECTOR. 

dry  steam  after  expanding  from  135  to  4  pounds  absolute,  is 
0.8243;  from  the  Steam  Tables,  r,  the  heat  of  vaporization 
=  1007.2;  therefore, 

1007.2  x  0.8243  —  830.23 
121.09  —  (  150°  —  32°  )  —     3.09 

833.32    Thermal  Units. 

remaining  in  the  steam,  and  given  out  to  the  13  pounds  of 
water  during  condensation  ;  this  will  raise  the  temperature 
833.32  -f-  13  =  64.1°,  or  in  different  form, 


(29) 


so  that  the  sum  of  64.1°  and  17.83°,  will  be  equal  to  the 
total  rise  in  the  temperature  of  the  feed  as  the  water  passes 
through  the  injector,  or, 


Adding  these  two  values  17.83  -f  64.1  =  81.93  as  the  total 
increase  in  temperature,  the  delivery  temperature  will  be 
68.0  +  81.93  =  1W9-930 

which  is  the  same  as  found  experimentally. 

Expressing  these  results  algebraically,  by  adding  (24)  (25) 
and  (29),  subtracting  the  work  required  to  force  the  mixture 
into  the  boiler  (26),  and  equating  to  the  increase  in  the  tem- 
perature of  the  feed  water  (30), 

f  r  +      —  xr  —      )+_?!(       +  a_;n- 


Reducing  and  cancelling  and  changing  the  form  in  order  to 
find  the  value  of  W,  we  have 


q,  ~  t,  ~  -~ 


(32) 


H-  34  -  h 

4~/lH"  778 

From  this  equation  have  disappeared  the  terms  denoting  the 

heat  in  the  steam  after  expansion,  and  the  important  func- 


THE  ACTION  OF  THE  INJECTOR.  83 

tions  remaining,  are  the  total  heat  in  the  steam  in  its  initial 
condition  and  the  temperature  of  the  feed  and  delivery.  Let 
P  denote  gauge  pressure ;  then,  discarding  unessential  terms, 

*-,  rv  +  ft  +  32  -  /,  -  (.003)  P 
~^-^+~(^3}P~ 

This  equation  enables  us  to  determine  the  weight  of  water 
delivered  per  pound  of  steam  by  any  injector  by  simply  ob- 
serving the  temperatures  of  the  feed  and  delivery  and  the 
initial  pressure  of  the  steam,  and  substituting  the  proper 
values  from  any  Steam  Table  ;  or,  knowing  the  area  of  the 
steam  nozzle,  the  discharge  may  be  calculated  by  (12), 
which,  multiplied  by  the  ratio  W,  gives  the  capacity  of  the 
injector. 

As  brass  is  a  good  conductor  of  heat,  there  is  always  a 
certain  amount  of  heat  transmitted  through  the  walls  sepa- 
rating the  steam  and  feed  chambers,  which  increases  the 
temperature  of  the  delivered  water.  This  heat,  being  ab- 
stracted from  the  steam,  renders  the  discharge  through  the 
nozzle  more  or  less  wet,  and  reduces  the  quantity  and  velocity 
at  the  time  of  impact ;  if  excessive,  it  seriously  affects  the 
ability  of  the  injector  to  receive  feed  water  at  a  high  temper- 
ature, and  also  diminishes  the  range  of  capacities.  This 
heat  appears  in  the  difference  (/2  —  O,  and  this  term  may  be 
taken  as  a  good  test  of  the  practical  working  qualities  of  an 
injector. 

Probably  the  most  satisfactory  formula  that  could  be 
devised  to  cover  the  action  of  the  injector,  would  contain 
terms  denoting  the  volumes  of  the  steam,  feed  water  and  the 
combined  jet,  and  based  upon  the  exchange  of  momenta 
between  the  moving  masses.  If  limited  to  the  simple  case 
of  complete  condensation  of  the  actuating  steam,  this  could 
easily  be  solved,  and  this  analysis  was  in  fact,  followed  in' 
the  discussion  at  the  opening  of  this  chapter,  and  the  sizes 
of  the  various  orifices  calculated  ;  but  where  only  partial 
condensation  is  effected  an  uncertain  element  is  introduced 
that  can  only  be  approximated  by  a  formula  based  upon  the 
phenomena  supposed  to  take  place  within  the  combining 
tube  and  then  introducing  coefficients  to  make  the  results 


84  THE  GIFFARD  INJECTOR. 

conform  to  actual  experiments.  The  percentage  of  steam 
mixed  with  the  water  at  the  time  of  entrance  to  the  delivery 
tube,  and  uncondensed,  cannot  easily  be  determined,  as  the 
temperature  of  the  jet  at  that  time  is  lower  than  when 
measured  in  the  boiler  pipe,  and  both  the  temperature  and. 
the  pressure  should  be  known  for  its  correct  determination. 
The  mechanical  efficiency  of  the  injector  can  be  found  by 
comparing  the  results  of  some  of  the  equations  already 
given  ;  in  the  previous  example  used  to  illustrate  the  form- 
ulae, the  work  of  forcing  14  pounds  of  water  against  a  head 
of  141  pounds,  amounted  to  5.97  thermal  units,  whereas  the 
total  energy  expended,  which  is  the  sum  of  (24)  and  (25)  = 
237.82  thermal  units,  so  that  the  efficiency  is 


But  the  remainder  of  the  energy  is  not  wasted,  but  trans- 
formed to  heat  and  absorbed  by  the  feed  water. 

The  maximum  capacity  of  an  injector  is  almost  entirely  a 
question  of  proper  proportions  and  efficient  action  of  the 
impinging  jet,  so  that  its  value  may  be  determined  by  equa- 
tion (21).  The  minimum  however  is  determined  by  the 
admissible  temperature  of  the  delivered  water  that  will  pass 
through  the  delivery  tube  without  overflow  ;  it  should  then 
be  determined  by  (33)  substituting  for  4  a  value  correspond- 
ing to  the  type  of  injector.  For  a  single  overflow  injector, 
/2  would  be  about  190°,  but  for  two  openings  from  the  combin- 
ing tube  into  the  same  chamber,  probably  215°,  at  60  or  80 
pounds  pressure.  If,  as  an  example,  the  case  is  taken  of  an 
injector  receiving  steam  at  60  pounds,  feed  70°,  and  a  de- 
livery temperature  of  190°,  we  have  from  (33), 

*-,  n  +  ft  —  (190°  —  32°)       898.8*1-  276.9  -  158° 
--  ~" 


If  the  delivery  temperature  at  the  maximum  capacity  is  125°, 
the  value  of  W  would  be  19.69,  and  the  ratio  of  the  mini- 
mum to  the  maximum  would  be 

0>i  8.48 

_J-  X  ico  =  -      6-  X  ioo  =  43  per  cent., 


THE  ACTION  OF  THE  INJECTOR.  85 

which  is  fairly  good,  although  if  the  injector  were  so  con- 
structed that  the  highest  delivery  could  reach  212°,  the 
minimum  would  be  reduced  to  7.23,  which  would  be  36  per 
cent,  of  the  full  capacity. 

The  highest  admissible  feed  temperature  is  difficult  to  cal- 
culate without  determining  the  special  coefficients  for  each 
case,  which  can  only  be  done  experimentally.  The  wTarmer 
the  feed  water,  the  greater  the  weight  necessary  to  condense 
a  given  weight  of  steam  and,  therefore,  the  heat  equation 
must  be  used  ;  on  the  other  hand,  the  power  of  the  steam 
for  forcing  water  through  the  delivery  tube  is  diminished  on 
account  of  its  reduced  terminal  velocity  owing  to  the  change 
in  pressure  w7ithin  the  combining  tube,  so  that  its  mo- 
mentum, and  the  rapidity  of  its  absorption  by  the  water  jet 
is  lessened  and  the  density  of  the  mixture  reduced.  Equa- 
ting the  equation  of  momentum  (21)  to  (33)  and  solving  for 
A  gives, 

-zO-(*1n  +  ?i  +  32°-'2)  (v  —  KvJi 
—~ 


By  way  of  illustration,  take  experiment  (</)  in  Table  VII  ; 
under  these  conditions,  the  mean  vacuum  in  the  combining 
tube  is  io|",  or  9^-  pounds  absolute  pressure,  which  gives  a 
terminal  velocity  to  the  steam  of  3050  feet  per  second.  The 
water  entering  the  combining  tube  has  a  velocity  vt  due  to 
the  low  internal  pressure  which  is  equal  to 


(  14.69  —  9.5  )  X  2  31  =  27.76  feet 
As  we  are  determining  the  extreme  capacity  of  the  instru- 
ment, it  will  be  assumed  that  the  mixture  has  just  sufficient 
power  to  enter  the  boiler  ;  its  velocity,  vt  .will  therefore  be 


*  34.69  —  9o  )  X  2.42  =139-7  feet  ; 
from  the  table,  K  =  0.473  an^  the  delivery  temperature 
/2  =  226°  ;  substituting  these  values  in  (34), 

226  (°473  x  3°5°  ~  ^9-7  ^ 


o-473  X  3050—  139-7 


which  agrees  very  closely  with  the  result  found. 


86  7*HE   GIFFARD   INJECTOR. 

The  actual  cause  of  the  inefficiency  of  the  injector  from  a 
mechanical  point  of  view,  is  due  to  its  dependence  upon  the 
principle  of  impact  for  the  transfer  of  the  actual  energy  of 
the  steam  to  the  moving  water;  this  induces  such  an 
enormous  waste  of  power  that  its  use  as  a  pump  for  raising 
water  is  out  of  the  question  except  in  such  cases  where 
economy  of  steam  is  no  object,  or  where  the  heating  of  the 
delivered  water  may  be  advantageous.  The  momentum  of  a 
body  is  equal  to  the  product  of  the  mass  by  the  velocity,  and 
the  resultant  velocity  after  impact,  is  equal  to  the  sum  of  the 
momenta  of  the  two  bodies  divided  by  the  sum  of  their 
masses ;  on  the  other  hand,  the  actual  energy  is  proportional 
to  the  square  of  the  velocities.  Kven  if  there  were  no  loss 
of  momentum  in  the  injector,  yet  there  would  be  a  dissipa- 
tion of  energy,  owing  to  the  reduction  of  velocity ;  if  one 
pound  of  vSteam  moving  at  a  rate  of  3000  feet  per  second 
strikes  9  pounds  of  water  at  rest,  and  imparts  all  its 
momentum,  the  resultant  velocity  of  the  mixture  would  be 
300  feet  per  second,  yet  the  energy  of  the  jet  of  water  and 
steam  would  only  be  -^  of  that  of  the  initial  steam ;  for, 

Energy  of  steam  (3ooo)aX  I        ~   10 

so  that  the  greater  the  difference  between  the  velocity  of  the 
steam  and  the  final  velocity  of  the  delivery,  the  greater  the 
loss  of  actual  energy ;  this  also  shows  that  the  lower  the 
terminal  velocity,  the  gfeater  may  be  the  weight  of  water 
delivered,  so  that  the  equation  simply  measures  the  efficiency 
as  a  pump  and  not  as  a  boiler  feeder. 

As  an  example,  the  efficiency  of  the  jet  will  be  calculated 
in  the  case  of  experiment  (a)  Table  IV  ;  the  velocity  of  the 
steam  is  3435  feet,  of  the  entering  water,  40  feet,  and  of  the 
jet,  165.3  feet;  the  weight  of  water  delivered  per  pound  of 
steam,  12  pounds;  therefore, 

C(3435)2,(40)2X  12-1      •"       (i6S-3J!_VI 
— t—  I     -/V  i     — —  /\     •!•$ 
2g                           2g                                              "2g 

KI  —  3  per  cent, 

and  from  this  value  there  is  not  much  variation  throughout 
the  ordinary  range  of  steam  pressures. 


THE  ACTION  OF  THE  INJECTOR.  87 

Probably  the  most  satisfactory  way  to  compare  the  in- 
jector as  a  boiler  feeder  with  a  direct  acting  steam  pump, 
will  be  to  take  an  example  in  which  the  actual  coal  con- 
sumption in  the  two  cases  can  be  compared.  No  allowance 
will  be  made  for  the  advantages  which  may  be  claimed  for 
either  method  in  the  way  of  convenience  of  operation  or  for 
economy  of  maintenance. 

A  steam  boiler  evaporates  10  pounds  of  water  from  and  at 
212°  per  pound  of  coal,  and  it  is  required  to  deliver  3000 
pounds  of  steam  per  hour  at  80  pounds  pressure  ;  water 
supply  at  temperature  of  63°  ; 

(a)   The  Direct  Acting  Steam  Ptimp. 

As  the  boiler  receives  the  feed  water  at  63°,  the  actual 
evaporation  is 

—  ----  =  8.40  Ibs.  water  per  pound  of  coal  ; 
1213  —  63° 

where  966  is  the  latent  heat  of  one  pound  of  water  at  212°, 
and  1213  the  total  heat  above  o°  of  i  pound  of  steam  at  80 
pounds  gauge  pressure.  The  work  of  forcing  3000  pounds 
of  feed  water  into  the  boiler  per  hour,  or  50  pounds  per 
minute,  against  a  head  of  80  X  2.31  feet  is, 


33000 

where  2.31  is  the  height  of  a  column  of  water  at  a  tempera- 
ture of  63°,  equal  to  a  pressure  of  i  pound  per  sq.  in.  from 
Table  II.  According  to  experiments  made  by  Prof.  D.  S. 
Jacobus,  of  the  Stevens  Institute  of  Technology,  a  direct- 
acting  steam  pump  requires  under  these  conditions  150 
pounds  of  steam  per  horse  power  per  hour  ;  accepting  this 
figure,  an  additional  weight  of  feed  water  is  necessary  to 
supply  the  steam  for  the  pump  equal  to 

150  X  0.28  =  42  Ibs.  per  hour, 

and  to  force  this  weight  of  feed  water  into  the  boiler  requires 
0.585  pounds  of  steam,  determined  as  before,  making  an 
approximate  total  of  42.585  pounds  of  steam.  This  can  be 
calculated  precisely  by  the  following  equation,  where  y  is 
the  total  weight  of  steam  required  for  feeding  the  boiler  : 


88  THE  GIFFARD  INJECTOR. 

50  +  -r-  )  80  X  2.31  X  150 


=y  =  42.596  Ibs.  feed  per  hour. 


33,o°° 
The  total  weight  of  coal  used  by  the  boiler  is 

jooojf  J2.596  =  362.2I  lbs.  coal  per  hour. 

8.4° 

(£)   The  Injector. 

Feed  water  is  received  by  the  injector  at  63°  and  delivered 
to  the  boiler  at  123.4°.  The  evaporation  is,  therefore, 

—  9  --  -  —  ?—  =  8.865  Ibs.  of  water  per  pound  of  coal. 
1213—  123.4 

The  coal  required  to  supply  3000  pounds  of  steam  per'hour, 
-||g-  =  338.41  Ibs.  per  hour. 

Work  of  forcing  50  pounds  of  water  per  minute  into  the 
boiler, 

8o_x  _a.33_X  5?  =  Q  28      horse 
33,000 

where  2.33  is  the  height  of  an  equivalent  column  of  water 
at  the  new  feed  temperature  of  123.4°. 

As  i  horse  power  =  33,000  foot  pounds,  and  i  thermal  unit 
=  778  foot  pounds,  i  horse  power  is  equal  to  42.41  thermal 
units  ;  therefore  the  coal  required  per  hour  for  the  work  of 
feeding  the  boiler  with  the  injector  is 

0.2824  x  42.41  X  60 

fil  —        —  —  °-74  lbs-  Per  hour. 

Coal  required  to  supply  the  steam  that  is  applied  by  the 
injector  to  warming  the  feed  water, 

3^!  =  ,8.78  Ito.  per  hour. 


The  total  coal  used  in  this  case  is 

338.41  -j-  0.074  +  18.79  =  357-264  lbs.  per  hour. 
Saving  of  coal  when  the  boiler  is  fed  by  the  injector, 
362.21  —  357.264  =  4.94  lbs.  per  hour. 

!•&  per  cent. 

This  saving  of  4.94  pounds  of  coal  per  hour  corresponds 
to  the  heat  wasted  in  the  exhaust  steam  from  the  pump  and 
which  is  returned  to  the  boiler  by  the  injector. 


UNIVERSITY 


CHAPTER    VIII. 

APPLICATIONS  OF  THE  INJECTOR— FOREIGN  AND  AMERICAN 

PRACTICE — DESCRIPTION  OF  VARIOUS   PATTERNS 

OF  INJECTORS. 

A  TECHNICAL  classification  of  the  various  patterns  of 
injectors  would  be  made  according  to  the  essential  features 
embodied  in  the  construction,  similar  to  the  method  pursued 
in  Chapter  II,  but  as  far  as  practical  considerations  are  con- 
cerned, the  distinctive  feature  is  the  presence  or  absence  of  a 
partial  vacuum  in  the  suction  pipe  at  the  time  of  starting.  This 
may  be  produced  by  an  auxiliary  jet  of  steam,  or  by  introduc- 
ing the  proper  proportion  between  the  area  of  the  main  steam 
nozzle  and  the  upper  overflow  in  the  combining  tube ;  either 
of  these  systems  produces  a  vacuum  in  the  feed  pipe  prelimin- 
ary to  starting,  and  constitutes  the  inherent  characteristic  of 
the  Lifting  Injector ;  the  other  class,  requiring  a  pressure 
on  the  water  supply,  is  termed  Non- Lifting,  or  N.  L.  and 
permits  a  simplicity  of  construction  that  is  seldom  equalled 
in  the  other  form ;  either  class  may  be  self-adjusting,  single 
or  double  jet,  although  the  N.  L.  class  is  usually  made  in 
the  more  elementary  forms. 

The  injector  as  a  boiler  feeder  has  been  successfully  ap- 
plied to  all  kinds  of  service,  locomotive,  stationary,  marine, 
traction  engines,  etc.,  although  it  is  to  the  first  named  that 
it  has  proved  itself  most  useful,  and  for  locomotive  boilers 
has  superceded  all  other  devices.  For  stationary  service, 
the  non-lifting  is  used  whenever  a  head  of  water  is  obtain- 
able, principally  on  account  of  the  simplicity  of  its  operation. 
For  large  marine  boilers,  the  injector  is  chiefly  used  in  case 
of  the  disability  of  the  pumps,  but  for  small  boats,  the  re- 
starting pattern  has  been  extensively  adopted.  This  kind 

89 


90  THE  GIFFARD  INJECTOR. 

is  also  used  on  traction,  logging,  and  road  engines,  where  its 
certainty  of  action  and  special  adaptability,  render  it  invalu- 
able for  the  rough  work  to  which  such  machines  are  applied. 

The  usual  division  of  all  the  different  forms  of  injectors 
resolves  into  a  question  of  location  relative  to  the  water 
supply.  A  non  lifting  injector  is  usually  tested  under  a 
head  of  about  two  feet,  and  will  operate  at  all  higher  pres- 
sures by  regulating  the  feed  valve ;  this  does  not,  however, 
give  an  increased  capacity  unless  the  steam  pressure  is 
raised.  For  the  locomotive  injector,  the  steam  pressure 
under  which  it  is  tested  and  for  which  it  is  proportioned  is 
about  120  pounds,  while  for  stationary  boilers,  60  pounds  is 
substituted,  although  either  arrangement  will  permit  a  wide 
range  of  working  pressures.  A  lifting  injector  will  of  course 
operate  with  the  feed  water  flowing  to  it,  but  the  N.  L. 
form  will  not  work  under  the  reverse  condition  unless  it  is 
first  primed,  and  then  only  with  reduced  capacity,  because 
the  entrance  area  to  the  combining  tube  is  too  contracted. 

Although  there  are  many  different  styles  specially  designed 
for  locomotive  service,  almost  all  correspond  to  one  of  two 
standards  of  capacity  and  position,  of  the  steam,  feed  and 
delivery  connections;  these  are  derived  from  the  form  of 
injector  manufactured  by  two  of  the  best  known  companies, 
viz.,  the  Sellers'  or  P.  R.  R.  standard,  and  the  Monitor,  or 
New  York  standard.  This  is  advantageous  in  many  ways, 
as  it  renders  injectors  interchangeable,  and  permits  a  careful 
and  accurate  comparison  of  the  relative  merits  of  the  various 
kinds  in  use. 

Neither  in  England  nor  on  the  continent  is  there  any 
attempt  at  uniformity,  nor  is  the  construction  limited  to 
regular  manufacturers  ;  several  railroads  have  designed  and 
now  make  injectors  for  their  own  use,  especially  adapted  to 
the  requirements  of  their  own  motive  power ;  of  the  two 
classes,  the  N.  L.  is  more  generally  adopted,  and  it  is 
usually  of  clumsy  design  and  differs  materally  from  those 
in  use  on  American  railroads.  Fig.  18  is  a  drawing  of  the 
form  used  by  the  Great  Eastern  Railway  of  England  and  is 
applied  to  both  passenger  and  freight  engines.  The  com- 


APPLICATIONS  OF  THE  INJECTOR.  91 

bining  tube  is  heavily  ribbed  and  forms  the  body,  having  its 
upper  end  spread  into  a  double  flange,  to  which  are  attached 
the  steam  and  feed  connections ;  on  one  side  of  the  main 
casting  is  a  lazy  cock  and  on  the  other  a  heavy  flange,  the 
casing  being  made  either  right  or  left  hand — depending  upon 
the  side  of  the  locomotive  for  which  it  is  intended — as  it  is 
bolted  in  a  horizontal  position  to  the  frame,  below  the  foot- 
board. Large  numbers  of  injectors  answering  to  this  general 
description  are  in  use,  yet  no  real  standard  prevails,  and  it 
appears  that  the  English  railway  managers  have  not  yet 
determined  to  their  own  satisfaction  the  most  advantageous 
position  upon  the  locomotive.  Many  manufacturers  carry 


Fig.  18 


in  stock  all  conceivable  forms  of  casings  for  their  standard 
tubes,  adapted  to  be  attached  to  any  kind  of  locomotive  in 
any  possible  position.  Many  of  the  original  Giffard  in- 
jectors are  yet  in  use,  and  are  still  giving  satisfaction ;  they 
are  usually  placed  directly  back  of  the  fire  box,  and  part 
way  through  the  foot  plate. 

The  most  advanced  English  practice  favors  bolting  the 
injector  on  the  back  plate  of  the  boiler,  with  self-contained 
steam  and  check  valves,  and  with  steam  and  delivery  pipes 
within  the  boiler.  This  arrangement  is  neat  and  compact. 
and  as  all  parts  are  protected  against  accident,  possesses 
some  advantages  over  the  practice  in  America  of  outside 


THE  GIFFARD  INJECTOR. 


connections.  Objections  urged  against  this  system  include 
the  heating  of  the  suction  pipe  and  consequent  difficulty  in 
starting,  and  also  the  rapid  closing  of  the  delivery  pipe 
within  the  boiler  when  the  feed  water  contains  lime  or  cal- 
careous material  in  solution.  This  is  due  to  the  great 
difference  in  temperature  between  the  water  in  the  boiler 
and  the  water  within  the  pipe,  which  causes  a  separation  of 
the  solids  held  in  solution  and  a  deposit  on  the  interior  sur- 


Fig.19. 


FEtO 


STEAM 


WATER 


OVE.RFLOW 


face  of  the  pipe.  With  clean  water  these  injectors  have 
given  good  satifaction,  and  as  they  are  growing  in  favor, 
one  made  by  Gresham  &  Craven  of  Manchester  is  shown  in 
Fig.  19.  This  form  is  inverted,  the  steam  passing  from  the 
dome  through  the  pipe  A'  to  the  chamber  A  ;  steam  dis- 
charging upward  from  the  nozzle  a,  raises  the  water  without 
the  necessity  for  a  priming  spindle,  as  the  sliding  combining 
tube  b  is  forced  up,  exposing  the  large  upper  overflow  of  the 


APPLICATIONS  OF  THE  INJECTOR.  93 

draft  tube  b' ;  the  entrance  of  the  feed  water  and  the  ensuing 
partial  vacuum  draws  the  tube  down  against  its  seat  and  pre- 
vents admission  of  air,  while  the  jet  passing  through  the 
delivery  tube  c  is  discharged  at  the  front  end  of  the  boiler 
by  the  copper  pipe  C.  This  instrument  belongs  to  the 
re-starting  class  and  is  easily  primed ;  all  the  tubes  may  be 
removed  when  the  boiler  is  under  steam  by  closing  the  at- 
tached valves,  and  removing  the  top  cap  D. 

Another  form  of  injector  that  is  somewhat  similarly  ar- 
ranged, is  extensively  used  on  the  London  &  Northwest 
Railway,  and  was  designed  by  the  Superintendent  of  Motive 
Power,  Mr.  F.  R.  Webb.  It  consists  of  an  inverted  set  of 
tubes  connected  to  a  check  valve  on  the  back  of  the  boiler, 
and  lying  as  close  to  it  as  possible,  but  set  low  down  and 
exposing  but  a  short  length  of  suction  pipe  to  the  heating 
action  of  the  fire-box  ;  the  combining  and  delivery  tubes  are 
rigidly  connected  and  moved  to  or  from  the  steam  nozzle  by 
a  convenient  handle  actuating  a  quick  thread  screw.  The 
parts  are  set  so  that  the  water  from  the  tank  will  flow 
through  the  overflow,  so  that  no  lifting  device  is  neces- 
sary. 

In  France  and  in  Italy,  non-lifting  injectors  of  the  Fried- 
man type  are  largely  used — in  the  latter  country,  almost 
exclusively.  From  information  furnished  by  the  Com- 
pagnie  de  1'  Est  of  France  fully  one-half  of  the  2441  injectors 
in  use  in  1887,  upon  its  lines  were  of  the  Friedman  pattern, 
and  upon  the  Chemin  de  Fer  de  1'  Etat,  over  1000  of  the  same 
style  were  in  service  in  sizes  varying  from  6  to  10  millimetres. 
During  the  last  few  years,  however,  many  of  the  French 
railroads  have  been  experimenting  with  injectors  of  Ameri- 
can manufacture,  and  this  has  led  to  the  extensive  use  by 
several  of  the  companies  of  the  Sellers'  "  Self- Acting  "  In- 
jector, which  is  now  replacing  those  of  foreign  design.  This 
injector  is  shown  in  Fig.  26. 

In  Germany  and  Austria,  a  diversity  of  styles  prevail,  the 
greater  number  being  non-lifting ;  even  the  Korting  double 
jet  is  there  applied  beneath  the  foot  board,  while  in  this 
country  it  is  used  almost  exclusively  as  a  lifter.  Other  well 


94  THE  G1FFARD  INJECTOR. 

known     patterns  are  the  Friedman,  Hasswell,  Pohlmeyer, 
Schaeffer  &  Budenberg,  and  Bohler. 

Returning  to  American  practice,  it  may  be  said  without 
question,  that  the  lifting  injector  is  the  standard  class,  as 
few  railroads,  except  in  some  parts  of  the  West  and  South, 
use  the  other  forms.  In  certain  localities  where  the  feed 
water  is  impregnated  with  lime,  non-lifters  are  retained  on 
account  of  the  facility  with  which  they  can  be  cleaned,  and 
they  are  frequently  used  in  combination  with  the  other  form, 
one  being  placed  on  each  side  of  the  engine.  The  chief 
disadvantage  urged  against  this  injector  is  that  it  is  out  of 
reach  of  the  hand  and  eye  of  the  engine-driver,  and  a 
sudden  drop  in  the  steam  pressure  or  a  careless  opening  of 
the  lazy  cock  when  the  steam  is  shut  off,  may  drain  all  the 
water  out  of  the  tank.  This  difficulty  can  be  remedied  by 
adding  an  extension  to  the  overflow  nozzle  and  raising  it 
above  the  water  level,  and  placing  it  where  it  may  be  con- 
tinuously observed.  This  has  been  applied  by  the  Nathan 
Manufacturing  Co.,  of  New  York,  to  a  modified  form  of 
their  W.  F.  Injector,  shown  in  Fig.  22.  All  non-lifting  in- 
jectors should  be  placed  so  as  to  receive  the  feed  water  under 
as  high  a  head  as  possible,  as  the  action  is  thus  rendered 
more  certain,  and  the  operation  of  starting,  when  the  pipes 
are  warmed  by  leaky  steam  valves,  is  much  facilitated. 

The  almost  invariable  position  of  the  lifting  injector  upon 
a  locomotive  is  directly  in  front  of  the  engine-driver,  placed 
part  way  through  the  front  cab  frame  so  that  the  operating 
handles  will  be  in  convenient  reach ;  the  second  injector 
usually  occupies  a  similar  position  on  the  other  side.  On 
the  Philadelphia  &  Reading  R.  R.,  where  the  camel-back 
engine  is  much  used,  the  second  injector  is  set  through  the 
back  frame  of  the  cab  and  within  easy  reach,  so  that  both 
feeders  are  under  instant  command.  Both  the  manner  of 
placing  the  injectors  upon  locomotives,  and  the  design  of 
the  instruments  themselves,  seem  to  be  more  carefully 
thought  out  in  this  country  than  elsewhere — unless  the 
most  recent  English  practice  be  an  exception — and  American 
manufacturers  are  still  striving  to  bring  the  injector  into 


APPLICATIONS  OF  THE  INJECTOR. 


95 


even  more  convenient  shape  and  to  render  its  action  more 
efficient. 

In  order  to  show  clearly  the  actual  construction  of  the 
interior  of  the  injector,  selections  have  been  made  from  the 
various  patterns  in  general  use  and  illustrations  will  be  given 
of  those  most  widely  known. 


96 


THE  GIFFARD  INJECTOR. 


Fig.  20  is  a  sectional  view  of  the 

SELLERS'  INJECTOR  OF  1876, 

which  contains  the  ingenious  self-adjusting  feature  described 
and  illustrated  on  page  15;  it  is  conveniently  constructed 
for  operating  and  for  repairing,  and  is  started,  regulated  and 
stopped  by  means  of  a  single  lever,  requiring  no  hand  ad- 
justment for  any  variation  in  the  pressure  of  the  steam, 
height  of  lift,  or  temperature  of  the  feed  water.  The  lifting 
is  effected  by  drawing  the  lever  H  back  a  short  distance 
until  the  resistance  of  the  main  valve  Xis  felt;  this  admits 
steam  to  the  hollow  spindle  C,  which  discharges  through 
the  delivery  tube  D,  and  produces  a  partial  vacuum  in  the 
suction  pipe  ;  when  water  appears  at  the  overflow,  the  lever 
is  pulled  all  the  way  back,  drawing  with  it  the  connecting 
rod  Z,,  closing  the  waste  valve  K  and  forcing  the  jet  to  enter 
the  boiler ;  the  regulation  of  the  capacity  is  effected  by  ad- 
justing the  position  of  the  lever  by  means  of  the  steel  latch 
V,  on  the  guide  rod/.  Moving  the  lever  changes  the  area 
of  the  steam  nozzle  by  altering  the  distance  which  the  taper 
spindle  is  inserted,  and  any  variation  in  the  weight  of  steam 
discharged,  immediately  induces  an  automatic  movement 
of  the  combining  tube  which  preserves  the  correct  ratio 
between  the  water  and  the  steam.  An  air  chamber  M, 
cored  in  the  body,  connects  with  the  column  of  water  in 
the  suction  pipe,  so  that  all  shocks  and  jars  will  be  ab- 
sorbed by  the  elasticity  of  the  air,  and  will  not  be  trans- 
mitted to  the  tube,  and  cause  the  injector  to  '"break"  or 
"  fly  off." 

The  following  Table  furnished  by  the  makers  gives  the 
maximum  capacity  of  this  injector  in  cubic  feet  per  hour: 


Size  of  Injector. 

Steam  Pressure. 

No.  3. 

No.  4. 

No.  5. 

No.  6. 

No.  7. 

No.  8. 

No.  9. 

No.  10. 

6olbs.    .   .   . 

30 

55 

86 

118 

161 

210 

269 

332 

120     "... 

40 

70 

112 

1  60 

218 

288 

357 

445 

APPLICATIONS  OF  THE  INJECTOR. 


97 


THE    MONITOR    INJECTOR. 

This  is  one  of  the  best  known  of  the  locomotive  injectors, 
and  is  a  modification  of  Friedman's  arrangement  of  tubes, 
with  an  improved  casing.  The  combining  tube  is  divided 
into  two  parts,  forming  an  upper  overflow  at  a  point  in  the 
tube  where  the  cross-section  is  about  the  same  as  that  of  the 
steam  nozzle ;  this  enables  the  injector  to  be  started  with 
great  facility,  and  the  air  to  be  drawn  from  the  suction  pipe, 
by  means  of  the  independent  ejector,  quickly  and  promptly. 


FIG.  21.     "  MONITOR.' 


H 


The  manipulation  is  as  follows :  opening  the  handle  Jt 
admits  steam  to  the  lifting  jet  which  discharges  through  the 
waste  pipe,  creating  a  strong  vacuum  ;  when  water  appears 
at  the  overflow,  the  handle  5"  opens  the  main  steam  jet  and 
the  water  is  forced  through  the  delivery  tube  into  the  boiler  ; 
with  high  pressure  steam,  this  draws  all  the  water  away 
from  the  lifting  jet,  and  clear  steam  blows  from  the  waste 
pipe  which  is  checked  by  closing  J\  with  low  steam  the 
water  supply  may  have  to  be  throttled  by  the  regulating 
valve  W  in  order  to  have  the  injector  "run  dry.''  This 
valve  is  also  used  to  adjust  the  capacity  to  suit  the  require- 
ments of  the  boiler,  and  permits  of  considerable  variation. 
7 


98 


THE  GIFFARD  INJECTOR. 


H31108  01 


APPLICATIONS  OF  THE  INJECTOR. 


99 


A  newer  form  of  this  injector  is  that  shown  in  Fig.  22, 
which  can  be  operated  with  a  lever  or  a  screw  handle  on  the 
steam  spindle,  and  obviates  the  necessity  for  the  starting 
jet  /,  by  the  use  of  the  taper  lifting-spindle  inserted  in  the 
steam  nozzle  which  discharges  through  the  combining  tube. 
The  steam  nozzle  is  made  larger  than  in  the  form  shown  in 
Fig.  21,  which  enables  it  to  operate  at  lower  steam  press- 
ures, while  a  movement  of  the  lever  forces  the  taper  spindle 
into  the  steam  nozzle  and  reduces  the  area  to  a  size  better 
suited  to  high  pressures;  the  range  of  steam  pressures 
through  which  the  injector  will  operate  satisfactorily  is 
much  increased  by  this  change. 

The  body  is  made  in  three  parts,  bolted  and  screwed 
together,  and  is  heavily  and  strongly  constructed  through- 
out. The  following  table  of  capacities  is  reduced  from  that 
given  in  the  catalogue  of  the  Nathan  Manufacturing  Co., 
and  applies  to  all  the  forms  of  the  Monitor  Injector,  and 
also  to  the  WF  pattern,  Fig.  23.  This  table  gives  the 
capacity  in  cubic  feet  per  hour  at  a  steam  pressure  of  140 
pounds  per  square  inch,  feed  temperature  60°  to  70°  Fahr., 
when  the  injector  is  placed  at  the  usual  height  of  lift  on  a 
locomotive  : 


Steam. 

No.  4. 

No.  5. 

No.  6.   '  No.  7. 

No.  8. 

No.  9. 

No.  10. 

No.  ii. 

No.  12. 

140  Ibs.  . 

73-3 

126.6 

1  66         240 

306 

386 

453 

506 

560 

Made  by  the  same  company  is  the 

NATHAN    WF    INJECTOR, 

designed  to  be  placed  below  the  foot-board  with  water  flow- 
ing to  it.  The  construction,  as  shown  in  Fig.  23,  is  very 
simple,  and  the  steam  nozzle  and  combining  tube  may  be 
easily  removed.  Steam  enters  at  the  top  of  the  casing  and 
the  water  passes  upward  from  the  bottom  through  a  cored 
passage  to  the  entrance  to  the  combining  tube ;  the  opening 
to  the  overflow  valve  is  indicated  in  the  cut  by  the  circle 
between  the  combining  and  the  delivery  tube,  and  the 


100 


THE   GIFFARD  INJECTOR. 


FIG.  23.    NATHAN  W  F. 


valve  body  may  be  placed  on 
either  side  of  the  body,  the 
opposite  opening  being  closed 
with  a  screw  cap.  The  pro- 
portions of  the  tubes  and  the 
arrangement  of  the  overflows 
are  similar  to  those  of  the 
Monitor  pattern,  and  the  list 
of  capacities  is  the  same. 

A  newer  form  of  the  non- 
lifting  injector  has  been  pro- 
vided with  a  waste  pipe  ex- 
tending above  the  water  level 
of  the  tank  and  into  the  cab, 
where  it  may  be  under  the 
constant  observation  of  the 
engine  driver,  who  is  thus 
able  to  notice  and  check  any 
tendency  to  waste.  The  tubes 
are  arranged  more  in  the  form 
of  those  shown  in  Fig.  22,  and  a  spindle  is  sometimes  pro- 
vided to  facilitate  starting. 

Fig.  24  is  a  sectional  view  of  the  American  form  of  the 
"  Korting  Universal,"  the 

"SCHUTTE    INJECTOR," 

which  belongs  to  the  double-jet  type.  It  has  no  overflows 
in  either  the  lifting  or  the  forcing  combining  tubes,  as 
the  starting  of  the  jet  is  effected  by  direct  communica- 
tion with  the  air  through  the  compound  waste  valve 
placed  vertically  over  the  nozzle  B.  With  this  instru- 
ment the  manipulation  is  as  follows  :  Drawing  the  lever 
from  A  to  B  transmits  the  pull  to  *the  valve  over  the 
lifting  steam  nozzle  by  means  of  the  bar  held  loosely 
between  the  caps  K  K ;  as  the  valve  of  the  forcing 
set  has  a  larger  area,  it  is  held  by  the  steam  pressure 
firmly  to  its  seat,  and  acts  as  a  fulcrum  for  the  lever. 
After  the  appearance  of  the  water  at  the  waste  pipe,  the 


APPLICATIONS  OF  THE  INJECTOR. 


101 


handle  is  drawn  further  out,  and  the  vertical  overflow 
valve,  connected  with  the  starting  lever  by  means  of  a  rod 
and  bell-crank  not  shown,  cuts  off  the  outlet  of  the  first  set 
and  diverts  the  water  through  the  forcing  combining  tube. 
The  second  steam  nozzle  is  then  opened  by  the  continued 
movement  of  the  starting  lever,  which,  during  the  latter 
part  of  its  stroke,  closes  the  waste  valve ;  the  jet  then  enters 
the  boiler.  Although  the  operation  has  been  divided  into 
several  steps,  the  motion  of  the  lever  is  practically  contin- 
uous and  the  starting  very  simple.  An  elementary  form  of 

FIG.  24.     "SCHUTTE." 


this  injector  was  shown  in  Fig.  4,  where  the  principle  em- 
bodied in  its  construction  was  explained  ;  reference  has 
been  already  made  to  the  peculiarities  of  construction  w^hich 
enable  this  type  of  instrument  to  receive  water  at  a  high 
feed  temperature  and  operate  through  a  wide  range  of  steam 
pressures  ;  at  60  pounds  steam,  the  permissible  temperature 
of  the  feed  water,  lifted  5  feet,  is  150°,  and  at  125  pounds 
steam,  135°. 

The  capacity  in  cubic  feet  per  hour  is  shown  by  the  fol- 
lowing table,  based  upon  the  following  conditions  :  Feed, 
80°,  lift  4  feet ;  at  65°,  the  values  will  be  increased  about  5 


102 


THE  GIFFARD  INJECTOR. 


per  cent.  ;  on  the  other  hand,  when  the  height  of  lift  is  10 
feet,  there  will  be  a  reduction  of  the  capacity  of  10  per  cent. ; 
at  15  feet,  25  per  cent. 


Steam. 

No.  i. 

No.  2. 

No.  3. 

No  3^ 

No.  4- 

No.  5. 

No.  6. 

No.  7. 

No.  8. 

No.  9. 

No.  10. 

30 

13 

20 

33 

46 

60 

75 

90 

128 

165 

195 

240 

60 

16.5 

25 

39 

57 

76 

98 

1  2O 

150 

195 

240 

2*5 

120 

21 

29 

48 

66 

86 

in 

136 

195 

25.  s 

300 

345 

150 

24 

31 

53 

73 

96 

123 

15° 

215 

282 

33° 

380 

In  the  injector  illustrated,  the  capacity  is  adjusted  to  the 
requirements  of  the  boiler  by  means  of  a  valve  placed  in  the 
suction  pipe,  but  the  more  recent  improvements  include  a 
small  taper  spindle  inserted  in  the  steam  nozzle  of  the  lifting 
set,  and  adjusted  by  a  handle  directly  under  the  starting 
lever.  This  varies  the  flow  of  steam  in  the  lifting  set, 
changing  the  amount  of  water  delivered,  and  materially  re- 
duces the  steam  consumption  at  the  minimum  capacity. 
It  is  so  arranged,  however,  that  the  lifting  power  of  the 
injector  is  in  no  way  affected,  for  the  water  can  be  raised 
and  forced  into  the  boiler  even  when  the  regulating  lever  is 
set  for  the  lowest  delivery  of  the  instrument. 

THE   BELFIELD    INJECTOR 

also  belongs  to  the  double-jet  type,  but  differs  from  the  pre- 
vious form  in  having  all  the  tubes  in  the  same  axial  line  ; 
suction  is  produced  by  the  hollow  cylindrical  spindle,  which 
is,  however,  never  entirely  withdrawn  from  the  first  steam 
nozzle,  so  that  the  entering  water  receives  impulses  from 
both  the  central  and  the  surrounding  jet.  After  passing  the 
first  delivery  tube,  the  feed  water  meets  the  discharge  from 
the  annular  second  jet,  opened  by  a  second  movement  of  the 
starting  lever ;  the  water  then  enters  the  boiler,  but  requires, 
in  order  to  obtain  more  positive  action  and  a  fair  minimum 
capacity,  the  tight  closing  of  the  waste  valve,  effected  by  the 
final  motion  of  the  lever.  Capacities  at  125  pounds  and  5 
feet  lift  are  given  in  the  following  table  ;  the  size  number  is 
arbitrary,  and  is  based  upon  the  capacity.  The  injector  will 


APPLICATIONS  OF  THE  INJECTOR. 


103 


operate  over  a  wide  range  of  steam  pressures,  and  gives  a 
fair  minimum. 


Steam. 

No.  3. 

No.  4. 

No.  5. 

No.  6. 

No.  7. 

No.  8. 

No.  9. 

No.  10. 

125  Ibs.  .  .  . 

40 

73 

"3 

160 

220 

290 

366 

452 

FIG.  25.     "  BEHELD  INJECTOR." 


A  notable  characteristic  of  the 

SELLERS'    SELF-ACTING    INJECTOR    OF   1887 

is  the  simplicity  of  its  construction  ;  its  special  features  are 
obtained  by  the  arrangement  of  its  overflows  and  the  pro- 
portions of  its  tubes,  instead  of  by  moving  parts  or  special 
valves.  In  common  with  the  self-adjusting  injectors  already 
described,  and  double-jet  injectors  in  general,  it  adjusts  and 
maintains  the  proper  supply  of  feed  water  for  each  pressure 
of  steam,  and,  in  addition,  re-starts  automatically  after  a 
temporary  interruption  of  the  water  or  steam  supply. 

As  may  be  seen  from  Fig.  26,  these  results  are  obtained  by 
means   of  the  following  arrangement  of  parts :    A  small 


104 


THE  GIFFARD   INJECTOR. 


APPLICATIONS  OF  THE  INJECTOR.  105 

annular  steam  nozzle  discharges  through  the  annular  area 
surrounding  a  central  forcing  steam  nozzle,  and  through  the 
overflow  spaces  in  the  combining  tube  ;  the  proportions  of 
these  parts  are  such  that  the  lifting  steam  nozzle  can  always 
produce  a  suction  in  the  feed  pipe  even  when  there  is  a 
discharge  from  the  main  steam  nozzle,  and  it  is  this  fact 
that  establishes  the  re-starting  feature.  When  the  feed 
water  rises  to  the  tubes,  it  meets  the  steam  issuing  from  the 
lifting  nozzle,  and  is  forced  by  it  in  a  thin  sheet  and  with  a 
high  velocity  into  the  combining  tube  of  the  forcing  set, 
without  the  necessity  for  the  interposition  of  a  divergent 
delivery  tube.  The  water  there  comes  in  contact  with  the 
main  steam  jet,  receives  an  additional  impulse,  and  the  mix- 
ture, reducing  in  cross-section  as  the  velocity  is  accelerated, 
rushes  past  the  overflow  openings  in  the  combining  tube  and 
passes  through  the  delivery  tube  into  the  boiler. 

The  self-adjusting  action  is  accomplished  by  the  change  of 
the  capacity  of  the  first  set  with  the  steam  pressure,  assisted 
by  the  influence  of  the  partial  vacuum  in  the  combining 
tube,  which,  being  communicated  to  the  .surrounding  overflow 
chamber  through  the  apertures  in  the  tubes,  assists  in  draw- 
ing an  additional  supply  of  feed  water  from  the  suction  pipe 
whenever  the  requirements  of  the  jet  are  increased  by  a  rise 
of  the  boiler  pressure.  This  maintains  a  constantly  increas- 
ing capacity  with  the  pressure,  and  gives  an  exceptionally 
large  range  of  boiler  pressures  with  which  the  injector  will 
work  efficiently. 

On  account  of  the  low  temperature  of  the  delivered  water, 
the  weight  of  water  forced  into  the  boiler  per  pound  of 
steam  is  unusually  high,  especially  at  locomotive  boiler 
pressures;  this  small  consumption  of  steam  permits -the 
grading  of  the  capacity  through  a  wide  range,  and  at  120 
pounds  steam,  when  lifting  i  foot,  the  capacity  may  be  re- 
duced by  throttling  the  feed  valve  to  36  per  cent,  of  the 
maximum  under  the  same  conditions ;  this  range  of  avail- 
able capacities  enables  the  injector  to  be  used  to  feed  the 
boiler  continuously  by  simply  adjusting  the  water  valve  to 
suit  the  requirements  of  the  boiler. 


106  THE  GIFFARD  INJECTOR. 

Not  only  is  the  range  of  capacities  dependent  upon  the 
minimum  expenditure  of  steam  to  perform  the  work  required, 
but  also  the  highest  admissible  temperature  of  the  feed  water  ; 
further,  as  this  is  dependent  also  upon  the  limiting  tem- 
perature of  the  mixture  that  will  pass  through  the  narrow- 
est part  of  the  delivery  tube  without  overflow,  it  follows 
that  an  injector  that  can  maintain  a  continuous  jet  at  a  tem- 
perature of  250°  at  the  minimum  capacity  without  wasting 
from  the  overflow  nozzle,  freely  opening  to  the  air,  is  able  to 
use  very  hot  water.  Actual  tests  when  lifting  i  foot  at  1 20 
pounds  steam,  show  a  limiting  temperature  of  124°  for  the 
automatic  action,  and  136°  when  the  waste  valve  is  held  to 
its  seat  by  throwing  over  the  cam  lever  ;  these  results  were 
obtained  with  fairly  dry  steam  and  without  special  care  in 
handling  ;  regulation  of  the  feed  valve  is  the  only  movement 
required  to  obtain  the  minimum  capacity. 

The  most  recent  improvement  in  this  form  of  injector  is 
shown  in  Fig.  26.  A  new  check  valve  has  been  introduced 
between  the  water  supply  and  the  overflow  chamber  for  the 
purpose  of  admitting  a  supplemental  supply  of  water  when- 
ever there  is  a  partial  vacuum  therein,  caused  by  the  incom- 
plete condensation  of  the  steam  in  the  upper  part  of  the 
combining  tube.  It  was  found  that  an  insufficient  amount 
of  water  passed  through  the  annular  lifting  tube  at  pressures 
above  160  Ibs.,  and  produced  a  high  vacuum  within  the  over- 
flow chamber.  This  vacuum  is  now  utilized  to  draw  in  an 
additional  supply  of  water,  which  enters  the  lower  tube  and 
passes  with  the  jet  into  the  boiler,  increasing  the  capacity 
about  24  per  cent,  at  1 80  pounds  pressure.  When  the  vac- 
uum in  this  chamber  is  less  than  that  in  the  suction  pipe 
this  check  valve  closes  automatically,  preventing  any  steam 
or  hot  water  entering  the  suction  pipe  during  the  operation 
of  priming. 

That  it  is  very  efficient  at  the  high  pressure  is  shown  by 
the  accompanying  table  of  capacities,  which  gives  rapidly 
increasing  figures  as  the  pressure  is  raised.  The  range  is 
good:  57  per  cent,  at  200  Ibs.,  and  63  per  cent,  at  120  Ibs. 


APPLICATION  OF  THE  INJECTOR. 


107 


A  full  and  complete  test  is  given,  page  134.  This  injector  is 
specially  designed  for  locomotive  service,  and  occupies  but 
little  room  in  the  cab ;  upon  removing  the  overflow  sleeve 
after  unscrewing  the  jam  nut,  the  body  may  be  placed 
through  a  round  hole  in  the  front  cab  frame,  allowing  only 
the  steam  and  feed  pipes  and  manipulating  handles  to  pro- 
ject into  the  cab.  Each  size  of  injector  is  named  from  the 
diameter  of  the  delivery  tube  expressed  in  millimetres,  and 
the  capacity  is  given  in  the  following  table  in  cubic  feet  per 
hour  at  the  ordinary  steam  pressures  employed ;  height  of 
lift.  5  feet. 


SIZE. 

30 

67 

60 

89 

I2O 

160 

i33 

200 

138 

5& 

121 

^ 

98 

129 

I76 

i93 

2O2 

1\ 

130 

172 

234 

258 

268 

345 

*i 

167 

221 

301 

332 

9^ 

209 

276 

376 

410 

425 

101 

255 

338 

460 

505 

527 

»i 

305 

405 

55i 

607 

630 

THE    METROPOLITAN    INJECTOR. 

This  injector  is  of  the  double-tube  class.  It  is  provided 
with  a  closed  overflow,  and  designed  with  a  view  of  obtaining 
a  double- tube  injector  without  outside  attachments,  rendering 
the  construction  simple.  The  lifting  apparatus  lifts  the  water, 
delivers  it  under  pressure  to  the  forcing  apparatus,  which  in 
turn  discharges  it  into  the  boiler.  There  is  a  double  steam 
valve  for  successively  admitting  steam  to  the  lifting  appara- 
tus and  to  the  forcing  apparatus  ;  to  the  stem  of  the  main 
steam  valve  the  overflow  valve  stem  is  rigidly  connected  by 
means  of  a  cross-head.  The  overflow  valve  stem  passes 


108 


THE   GIFFARD   INJECTOR. 


APPLICATION  OF  THE  INJECTOR.  109 

through  a  cored  passage  in  the  injector,  which  opens  directly 
into  the  atmosphere  through  the  overflow  passage.  By  the 
form  of  valve-stem  used,  and  the  means  for  operating  it,  an 
overflow  valve  of  the  simplest  type  can  be  used. 

The  overflow  valve  seat  is  made  removable  from  the  casing, 
thus  facilitating  repairs.  The  manufacturers  state  that  this 
injector  can  be  started  with  25  Ibs.  steam  pressure,  and  with- 
out any  adjustment  or  regulation  of  any  kind,  can  be  operated 
at  steam  pressures  up  to  275  Ibs.  Also,  that  these  injectors 
will  take  feed- water  at  145  to  150  degrees  F.,  with  TOO  Ibs. 
steam  pressure  ;  at  142  degrees  F.  with  125  Ibs.  steam  pres- 
sure ;  at  135  degrees  F.  with  150  Ibs.  steam  pressure  ;  at  130 
degrees  F.  with  175  Ibs.  steam  pressure,  and  at  125  degrees 
F.  with  200  Ibs.  steam  pressure.  The  capacity  is  regulated 
by  increasing  or  decreasing  the  amount  of  steam  to  the 
lifting  apparatus,  by  adjusting  the  small  hand  wheel  below 
the  operating  lever 

Its  operation,  briefly,  is  as  follows :  The  lever  being 
drawn  back  slightly  opens  the  steam  valve  to  admit  steam 
to  the  lifting  apparatus  ;  steam  passing  through  the  lifting 
apparatus  raises  the  automatic  valve,  which  gives  instant 
relief,  and  thus  enables  the  injector  to  lift  the  water  promptly. 
As  soon  as  the  water  is  lifted  it  takes  the  same  course  as  the 
steam,  passes  out  through  the  overflow,  thus  filling  the 
water  passages  of  the  injector.  As  soon  as  water  appears  at 
the  overflow  the  lever  is  drawn  back  admitting  steam  to 
the  forcing  apparatus,  which  seats  the  automatic  overflow 
valve,  owing  to  the  increased  pressure  on  top  of  this  valve, 
and  finally  closes  the  overflow  valve  of  the  forcing  appar- 
atus, thus  turning  the  water  from  the  overflow  into  the 
boiler. 

The  injectors  already  illustrated  comprise  the  most  promi- 
nent in  use  upon  American  locomotives,  and  contain  special 
features,  which  are  in  many  cases  duplicated,  though  perhaps 
in  a  less  efficient  degree,  in  other  patterns ;  special  mention, 
however,  should  be  made  of  the  Hancock  Inspirator,  Gar- 
field,  Mack,  Eynon  Evans  and  Ohio  Injectors,  but  it  would 


110  THE   GIFFARD   INJECTOR. 

occupy  too  much  space  to  illustrate  these  and  all  the  other 
patterns  in  use,  and  those  given  embody  the  most  successful 
application  of  the  essential  principles.  Many  of  these  in- 
jectors are  also  used  upon  stationary  boilers,  yet  they  are 
more  generally  applied  to  railroad  service. 

The  following  have  been  selected  from  the  great  variety 
of  injectors  designed  for  stationary,  traction  and  marine 
boilers  as  containing  special  features  of  interest ;  almost  all 
are  well  known,  and  are  carefully  designed  and  accurately 
manufactured. 

FIG.  28. 


Almost  all  single-jet  injectors  designed  for  stationary  or 
marine  service,  are  arranged  to  start  through  a  lower  over- 
flow or  aperture  placed  between  the  mouth  of  the  delivery 
tube  and  the  lower  end  of  the  combining  tube.  An  excep- 
tion, however,  is  the 

PENBERTHY  SPECIAL 

which  is  shown  in  Fig.  28,  and  described  by  the  manufac- 
turers as  an  Auto-positive  Injector.  The  usual  upper  over- 
flow, characteristic  of  re-starting  injectors  is  used,  but  the 
combining  and  delivery  tubes  are  made  continuous,  without 
spill  holes  or  separating  space.  The  jet,  therefore,  starts 
through  the  delivery  tube,  as  tte  final  or  pressure  chamber 
H  has  free  access  to  the  air  when  the  valve  H,  is  raised  from 
its  seat  on  the  bushing  M  whenever  the  valve  K  opens.  The 


APPLICATION  OF  THE  INJECTOR.  Ill 

action  of  starting  is  as  follows  :  Steam  is  admitted  through 
the  upper  right-hand  branch  to  the  nozzle  X  and  discharging 
through  the  draft-tube  G,  produces  a  vacuum  in  the  suc- 
tion pipe ;  the  discharging  steam  forces  the  automatic  valve 
K  against  the  end  of  the  pressure  valve  L,,  which  is  thus 
held  open  to  permit  free  outlet  of  steam  and  water  from  the 
chamber  H ;  this  is  made  possible  by  having  the  area  of  K 
about  twice  that  of  I,.  When  the  correct  proportions  of 
water  and  steam  are  admitted  and  the  jet  is  formed,  the  pres- 
sure in  the  chamber  containing  the  upper  overflow  is  changed 
to  a  partial  vacuum,  which  draws  the  automatic  valve  K  to 
its  seat  and  allows  the  pressure  valve  L,  to  close,  compelling 
the  feed  to  pass  under  the  check  valve  P  and  into  the  boiler. 

The  construction  of  the  injector  is  very  simple  and  easily 
understood.  As  it  has  no  lower  overflow,  the  action  is  sim- 
ilar to  that  of  a  positive  or  closed  overflow  injector,  so  that 
the  overflowing  temperature  corresponds  to  the  breaking 
temperature  of  the  ordinary  single  jet  pattern.  The  range 
of  steam  pressure  is  said  to  be  good ;  the  minimum  capac- 
ity is  obtained  by  throttling  the  water  supply,  for  which 
purpose  a  valve  must  be  placed  on  the  suction  pipe. 

A  sectional  view  of  the 

SELLERS'    RESTARTING    INJECTOR. 

is  given  in  Fig.  29.  The  branches  for  steam,  water  supply 
and  delivery  to  the  boiler  are  conveniently  arranged,  so  that 
all  the  pipes  may  be  placed  close  against  the  boiler  wall. 
The  overflow  is  directly  under  the  water  branch  and  can  be 
provided  with  a  drip  funnel  and  discharge  pipe,  without 
bending  or  springing  the  other  pipe  connections.  The 
steam  nozzle  and  delivery  tubes  are  screwed  into  the  body, 
and  do  not  depend  upon  the  pressure  of  the  steam  or  of  the 
delivery  to  hold  them  in  place,  so  that  there  is  no  danger  of 
leakage  at  these  important  shoulders.  The  body  and  tubes 
are  constructed  of  the  best  bronze  and  are  designed  to  give  the 
longest  service  with  the  least  amount  of  attention  and  repair. 
The  injector  is  simply  constructed,  and  contains  but  few 


112  THE  GIFFARD  INJECTOR. 

parts.  It  is  perfectly  automatic  in  its  action,  restarting 
instantly  after  a  temporary  interruption  of  the  steam  or  water 
supply.  It  raises  the  feed  promptly  on  long  lifts,  with  hot 
or  cold  pipes,  and  gives  a  good  range  of  capacities.  Steam 
enters  at  the  top  and  passing  down  through  the  steam  nozzle, 
No.  3,  discharges  through  the  draft  tube  into  the  overflow 
chamber  and  thence  to  the  air,  lifting  the  water  to  the  Injec- 
tor. The  partial  vacuum  caused  by  the  condensation  of  the 
steam  within  the  combining  tube  raises  bushing  No.  5  up 

FIG.  29. 


against  the  draft  tube  and  holds  the  lower  bushing,  No.  6, 
against  the  delivery  tube,  thus  preventing  the  admission  of  air. 

Upon  removing  the  cap  at  the  lower  end  of  the  body  the 
end  of  the  delivery  tube  will  be  seen  projecting  below  the 
lower  face  of  the  body,  so  that  a  monkey  wrench  may  be 
used  to  unscrew  this  tube,  drawing  out  the  tubes  and  the 
overflow  bushings  at  the  same  time. 

The  size  numbers  of  these  injectors  are  based  upon  the 
diameter  of  the  delivery  tube  expressed  in  tenths  of  milli- 
metres; No.  16,  for  instance,  is  IT"?  millimetres  in  diameter. 


APPLICATION  OF  THE  INJECTOR.  113 

For  all  ordinary  cases,  this  injector  requires  no  adjustment 
and  will  work  satisfactorily  from  40  to  100  pounds  steam, 
water  flowing  from  a  tank  or  from  the  city  mains,  or  when 
lifting  any  distance  up  to  15  feet.  If  it  is  necessary  to  use 
the  injector  continuously  at  15  or  20  pounds,  the  small  ring 
placed  under  the  steain  nozzle  should  be  removed,  and  the 
steam  nozzle  screwed  down  closer  to  the  draft  tube.  For 
150  pounds  steam  and  very  high  lifts  and  feed  temperatures, 
a  greater  distance  is  required  between  the  steam  nozzle  and 
the  draft  tube,  and  a  supplemental  ring,  supplied  with  the 
injector,  set  in  place,  permitting  a  wide  range  of  working 
pressures.  The  range  of  capacities  is  good,  and  warm  water 
can  be  fed  to  the  boiler. 
Fig.  30  is  a  section  of  the 

"  RUE  INJECTOR  "  (LITTLE  GIANT) 

with  which  the  experiments  were  made  which  were  tabu- 
lated on  page  47.  This  instrument  has  a  movable  combin- 
ing tube  by  which  the  water  area  may  be  regulated  for  any 
steam  pressure  or  desired  change  in  the  capacity,  and  this  is 

FIG.  30.     "Rui?." 


effected  by  moving  to  the  right  or  left  the  hand-lever  ful- 
crumed  on  the  body.  When  arranged  as  a  lifting  injector, 
a  separate  steam  jet  is  added,  either  in  the  form  of  a  central 
spindle  discharging  through  the  combining  tube  or  a  special 
nozzle  placed  in  the  waste  pipe.  The  advantage  of  the 


114 


THE  GIFFARD  INJECTOR. 


adjustable  water  area  has  already  been  described  in  detail, 
so  that  the  merit  of  this  feature  does  not  need  further  re- 
mark. Outside  stuffing  boxes  permit  absolutely  tight  joints 
between  the  water  and  overflow  chambers  and  the  atmos- 
phere, so  that  no  leakage  of  either  steam  or  water  need 
occur. 

Another  simple   form   of  injector,  but  which  has  fixed 
nozzles,  shown  in  section  in  Fig.  31,  is  the 

SELLERS'   F.  N.   INJECTOR    OF    1885. 

In  this  injector  the  upper  and  lower  overflows  are  so  ar- 
ranged in  the  combining  tube  that  it  is  automatic  in  its 
starting  action,  and  gives,  in  addition,  a  strong  vacuum, 
suitable  for  high  lifts,  when  the  steam  displacing  spindle  is 
run  slowly  out.  The  form  of  this  spindle  also  allows  of  a 
regulation  of  the  steam  supply  when  the  water  valve  is 
throttled,  lowering  the  delivery  temperature  so  as  to  give  at 

FIG.  31.    SKIVERS'  F.  N.  INJECTOR  OF  1885. 


60  pounds  steam,  a  minimum  capacity  of  25  per  cent,  of 
the  maximum.  The  list  of  capacities  conforms  closely  to 
that  of  the  Sellers'  1876  pattern,  yet  the  permissible  tem- 
perature of  the  feed  water  is  higher  at  the  lower  steam 
pressures;  at  65  pounds,  for  instance,  feed  at  136°  maybe 
used  when  flowing  to  the  injector  under  a  small  head,  with- 
out interfering  with  the  automatic  action,  and  this  may  be 
increased  to  150°  if  the  waste  valve  is  screwed  down.  The 


APPLICATIONS  OF  THE  INJECTOR. 


115 


tubes  are  removed  from  the  body  for  cleaning  or  repairs  by 
the  motion  of  unscrewing  the  end  cap,  without  the  necessity 
of  breaking  any  of  the  pipe  connections ;  water,  steam  and 
delivery  check  valves  are  alt  contained  in  the  body,  so  that 
the  injector  can  be  used  either  as  a  lifter  or  a  non-lifter. 

An  ingenious  device  by  which  the  area  of  the  water 
entrance  to  the  combining  tube  can  be  varied  without  the 
use  of  a  stuffing-box,  is  illustrated  in  Fig.  32,  a  sectional 
view  of  the 

METROPOLITAN    INJECTOR. 

The  operation  is  as  follows :  Rotating  the  handle  K  opens 
the  steam  valve  and  lifts  the  feed  water  by  the  strong  suc- 
tion produced  by  the  discharge  around  the  plug  M  passing 
through  the  draft  tube ;  when  this  plug  is  entirely  with- 

FIG.  32.     "METROPOLITAN," 


drawn,  the  full  area  of  the  nozzle  is  given  and  the  jet  is 
driven  into  the  boiler.  If  the  steam  pressure  is  high  or  the 
height  of  lift  is  great,  the  usual  supply  area  of  the  combin- 
ing tube  will  be  insufficient,  and  the  spindle  must  be  drawn 
against  the  rear  stop,  pulling  the  steam  nozzle  with  it  until 


OF  THB 


116 


THE  GIFFARD  INJECTOR. 


the  collar  on  5  strikes  against  the  back  wall  of  the  water 
chamber.  For  low  steam,  the  spindle  is  screwed  until  the 
collar  of  the  steam  nozzle  reaches  the  inner  stop,  when  the 
pressure  of  the  steam  holds  it  firmly  in  its  place.  Care  must 
be  taken  to  preserve  tight  joints  between  these  faces,  so  that 
no  leakage  can  occur  between  the  steam  and  feed  chambers, 
as  this  will  not  only  reduce  the  lifting  powers,  but  also  the 
capacity  of  the  injector. 

An  English  invention  that  has  been  used  in  this  country 
for  some  years  on  portable,  marine  and  stationary  boilers, 
is  the 

GRESHAM    RE-STARTING; 


FlG.  33- 


GRESHAM." 

STEAM 


its  interior  construction  is  simi- 
lar to  the  locomotive  injector 
shown  in  Fig.  19.  It  has  the 
same  form  of  movable  combin- 
ing tube  which  closes  the  upper 
overflow  when  the  injector  is  in 
action,  and  therefore  requires  no 
priming  device,  as  the  suction 
produced  by  the  discharge  of  the 
steam  through  the  draft  tube  is 
exceedingly  effective. 

An  ingenious  invention  for 
permitting  a  free  discharge  of 
steam  through  the  combining 
tube,  yet  giving  an  absolutely 
continuous  tube  to  the  moving 
water  jet,  is  the  flap  nozzle  sys- 
tem, invented  and  patented  by 
Hamer,  Metcalf  &  Davies,  of 

Manchester,  England,  in  1880,  and  shown  in  Fig.  34  as  a 

feature  of  the 

MANHATTAN    INJECTOR. 

This  form  of  tube  is  more  extensively  used  in  the  injectors 
using  exhaust  steam  than  the  usual  form  of  overflow  open- 
ings. The  tube  is  cut  longitudinally  at  its  middle  section  up 


DELIVERY 


APPLICATIONS  OF  THE  INJECTOR. 


11? 


to  a  point  near  the  steam  nozzle,  where  the  cross  section  of 
the  tube  is  sufficient  to  permit  easy  exit  for  water  or  steam. 
The  force  of  the  steam  striking  against  the  loose  hinged  por- 
tion, raises  it,  exposing  a  large  area  of  discharge ;  as  soon  as 
the  water  enters  the  tube,  the  partial  vacuum  caused  by  the 
condensation  of  the  steam  draws  the  tube  shut  and  holds  it 
in  that  position  as  long  as  the  jet  is  continuous.  This  sys- 
tem is  specially  advantageous  when  applied  to  exhaust 
injectors,  where  free  discharge  is  a  pre-requisite  condition, 
as  there  should  be  no  possible  danger  of  the  feed  water 


FIG.  34. 


MANHATTAN." 

STEAM 


WATER 

rising  in  the  steam  nozzle  when  the  jet  breaks,  as  it  might 
work  its  way  up  into  the  cylinder.  The  illustration  shows 
a  live  steam  injector,  re-starting  on  short  lifts,  but  intended 
primarity  as  a  non-lifter  ;  a  steam  valve  and  displacing  steam 
plug  can  be  inserted  in  place  of  the  cap  d  if  desirable.  All 
the  tubes  are  easily  removable,  and  care  should  be  taken  to 
allow  no  scale  or  sediment  to  be  deposited  upon  the  surfaces 
of  the  closing  jaws,  as  tips  is  apt  to  interfere  with  the  tight- 
ness of  the  joint  and  the  correct  alignment  of  the  tubes. 
The  different  parts  are  clearly  shown  in  the  cut— a,  b,  c, 
being  the  steam  nozzle,  combining  tube  and  the  delivery 


118 


THE   GIFFARD   INJECTOR. 


FIG.  ^5. 
EXHAUST  INJECTOR. 


tube ;  /  is  the  overflow  valve  to  prevent  air  being  drawn  to 
the  boiler  by  the  suction  of  the  jet  at  the  lower  overflow  or 
through  any  leak  between  the  joints  of  the  tubes. 

The   same    form   of  combining   tube   is   applied   to   the 
SchaefFer  &  Budenberg 

EXHAUST    STEAM    INJECTOR, 

illustrated  in  Fig.  35.  Here  the  steam 
nozzle  is  enlarged  to  meet  the  new  con- 
ditions, and  a  central  spindle  is  added, 
which,  when  the  pressure  of  the  boiler 
into  which  the  feed  water  is  delivered 
exceeds  75  pounds,  is  made  hollow, 
so  as  to  admit  a  supplemental  jet  of 
live  steam  from  the  boiler.  The  feed 
water  should  flow  to  the  instrument 
and  its  temperature  be  as  low  as  pos- 
sible, never,  under  any  conditions, 
above  90°  ;  with  the  supplemental  jet 
and  cold  feed  water,  the  injector  will 
feed  against  pressures  up  to  150 
pounds,  and  without  it,  against  90 
pounds;  increasing  the  temperature 
of  the  feed  diminishes  these  pressures 
somewhat. 

THE    PENBERTHY    INJECTOR, 

which  is  shown  in  Fig.  36,  also  belongs  to  the  re-starting 
class,  as  it  is  arranged  with  an  overflow  near  the  steam 
nozzle,  which  is  closed  when  the  injector  is  in  action  by  the 
loose  washer  T  sliding  upon  the  outside  of  the  combining 
tube  Y.  Steam  discharges  from  the  nozzle  R,  flows  through 
the  larger  opening  at  the  mouth  of  the  suction  tube  S,  and 
raises  the  water  to  the  feed  chamber,  the  inlet  branch  being 
at  the  side  of  the  body  facing  the  observer,  and  therefore 
not  appearing  in  the  drawing ;  the  partial  vacuum  caused  by 
the  condensation  of  the  steam  raises  the  washer  T  to  its  seat 
in  the  same  manner  as  the  combining  tube  in  the  Gresham 
Injector,  so  that  the  two  overflows  are  separated  and  no  air 


APPLICATIONS  OF  THE  INJECTOR. 


119 


can  enter,  even  if  the  waste  valve  P  should  leak  ;  this  valve 
is  made  large  enough  to  permit  free  discharge  for  the  steam 
without  producing  any  back  pressure  in  the  overflow  cham- 
ber, as  this  would  interfere  with  the  lifting  power  of  the 

FIG.  36.     <l  PENBERTHY." 


steam  jet.  The  following  tests  of  an  injector  of  this  pattern 
have  been  furnished  by  the  manufacturers,  but  were  made 
by  disinterested  experts — height  of  lift  =  3  feet : 


Limiting  feed  temperature  at  65  Ibs.  steam,  128°,  delivery  200 

75  "  121°         "         196 

U  85  „  II?0  « 

"         back  pressure  without  overflow  at  65  Ibs. ,  92  Ibs. 


196° 
200° 


75 
85 


103  ' 

112 


In  conclusion  it  may  be  said  that  the  construction  of  the 
injector  is  exceedingly  simple,   as   starting   is   effected   by 
opening  the   globe  valves   placed   on   the  steam   and   feed 
pipes. 
8 


120  THE   GIFFARD   INJECTOR. 

Among  other  well-known  patterns  of  injectors  designed 
especially  for  stationary  boilers  may  be  mentioned  the  Han- 
cock Inspirator,  Park,  Bberman,  Jenks,  SherrifT,  Buffalo, 
Globe ;  limit  of  space  prevents  the  insertion  of  descriptions 
and  illustrations  of  these  also,  and  a  sufficient  variety  has 
been  given  to  elucidate  the  principles  upon  which  all  are 
designed,  rendering  repetition  unnecessary. 


The  setting  of  an  injector  and  attaching  the  various  pipes 
to  a  stationary  boiler  are  much  more  simple  than  in  the  case 
of  a  locomotive.  When  required  to  lift,  the  chief  object  is 
to  obtain  a  position  as  near  the  level  of  the  water  supply  ?s 
possible,  without  sacrificing  convenience  of  handling,  as  the 
greatest  delivery  is  thus  obtained  and  less  care  and  precision 
required  for  starting  and  regulating.  Longer  service  will 
also  be  given  before  repairs  become  necessary,  because  the 
greater  the  tax  that  is  placed  upon  the  lifting  powers  of  an 
injector,  the  smaller  will  be  the  deviation  from  the  correct 
proportion  of  the  tube  which  will  affect  its  working.  The 
rate  at  which  the  delivery  decreases  as  the  lift  is  increased 
is  shown  by  Table  V,  on  page  76,  and  it  is  only  adjustable 
and  self-adjusting  injectors,  and  some  forms  of  the  double- 
jet,  that  are  exempt  from  this  rule.  The  suction  pipe  should 
therefore  be  as  short  and  direct  as  possible,  and  carefully 
tested  under  steam  pressure  to  detect  any  faulty  joints  or 
leaks  in  the  pipe  ;  if  very  long,  it  should  be  made  at  least 
one  size  larger  than  the  nipple  of  the  injector,  and  should 
be  sloped  on  long  horizontal  stretches  so  as  to  drain  toward 
the  well  without  air  or  water  pockets.  Foot  valves  are  not 
recommended,  but  strainers  should  be  used,  having  entrance 
holes  smaller  than  the  smallest  diameter  of  the  delivery 
tube,  with  an  aggregate  area  of  at  least  four  times  that  of 
the  suction  pipe. 

The  steam  pipe  should  be  attached  to  the  dome  of  the 
boiler,  or  connected  with  a  main  of  such  size  that  the  pres- 
sure of  the  contained  steam  will  be  constant  and  the  same  as 
that  in  the  boiler.  This  pipe  should  be  covered,  and  sup- 
plied with  a  pet-cock  for  draining  accumulated  water,  espe- 


APPLICATIONS  OF  THE  INJECTOR.  121 

ciallyif  the  conditions  under  which  the  injector  must  operate 
are  at  all  adverse.  Every  effort  should  be  made  to  supply 
as  dry  steam  as  possible,  and  this  can  only  be  obtained  by 
carrying  out  these  recommendations. 

The  delivery  pipe  should  of  course  be  short  and  direct, 
although  this  is  not  as  necessary  as  with  the  other  connec- 
tions ;  it  should  be  supplied  with  a  main  check  valve,  a  stop 
valve  and  a  pet  cock  for  draining.  The  vertical  length  of 
this  pipe  or  the  position  of  the  injector  relative  to  the  water 
level  of  the  boiler  is  comparatively  unimportant,  as  there  is 
always  an  excess  of  power  in  the  jet  more  than  sufficient  to 
overcome  any  ordinary  difference  in  level.  In  the  tests  of 
the  Penberthy  Injector  there  is  shown  to  be  an  excess  of 
counter  pressure  over  the  initial  of  28  pounds  at  75  pounds 
steam,  permitting  a  difference  in  level  and  friction  head  of 
about  56  feet,  far  greater  than  is  likely  to  occur  in  practice. 

All  steam  and  water  pipes  should  be  carefully  blown  out 
with  steam  to  free  them  from  dirt  and  scale  before  the  in- 
jector is  set  in  place,  and  all  pipes  should  be  bent  so  that 
the  unions  will  fit  squarely  in  their  seats,  requiring  no 
force  to  draw  them  to  place  when  the  coupling  nuts  are 
screwed  up. 

It  may  appear  that  needless  stress  has  been  laid  upon  the 
method  of  attaching  injectors,  and  that  unnecessary  refine- 
ments have  been  suggested,  yet  it  may  be  said  that  the 
advantages  arising  from  good  work  and  conscientious  atten- 
tion to  details  of  this  kind  more  than  compensate  for  the 
additional  outlay.  In  this  respect,  English  engineers  are 
much  more  particular  than  those  in  this  country  ;  the  gene- 
ral foreign  practice  is  to  substitute  pipes  bent  in  easy  curves 
for  all  cast  iron  elbows,  flanges  take  the  place  of  malleable 
iron  couplings,  while  the  general  solidity  and  care  mani- 
fested in  the  attachment  of  boiler  fittings  are  well  wrorthy  of 

imitation. 

BOILER   TESTERS. 

The  principle  of  the  injector  has  been  applied  very  satis- 
factorily to  the  testing  of  boiler  seams,  and  special  instru- 
ments are  made  for  this  purpose.  They  are  so  constructed 


122  THE  GIFFARD  INJECTOR. 

that  the  boiler  may  be  rapidly  filled  with  warm  water  and 
high  testing  pressure  then  applied,  even  though  the  jet  is 
actuated  by  low  pressure  steam. 

In  this  instrument,  two  sets  of  tubes  are  used,  one  for 
each  operation ;  the  primary  set  acts  as  an  ejector,  delivering 
between  600  and  700  cubic  feet  of  water  per  hour,  and  fills 
the  boiler  up  to  the  safety  valve;  all  openings  are  then 
closed,  and  the  smaller  set,  having  a  capacity  of  about  60 
cubic  feet  per  hour,  is  started,  and  the  pressure  in  the  boiler 
raised  to  the  point  desired;  this  secondary  set  is  propor- 
tioned like  an  injector,  but  has  a  much  larger  steam  nozzle 
than  would  be  ordinarily  employed,  as  the  excess  of  counter 
pressure  required  is  much  greater  than  in  the  case  of  an 
injector.  If  the  same  relations  that  obtain  in  the  exhaust 
injector  would  hold  true  at  70  pounds  steam,  testing  pres- 
sures of  450  pounds  would  be  produced,  for  with  an  absolute 
steam  pressure  of  14.69  pounds,  105  pounds,  or  seven  times 
the  initial,  can  be  obtained ;  but  in  this  case  the  area  of 
the  steam  nozzle  is  nearly  sixteen  times  that  of  its  delivery 
tube,  while  at  60  to  80  pounds,  4^  is  the  greatest  ratio  that 
can  be  used  efficiently.  The  usual  pressures  are  about  as 
follows : 

30  pounds  initial  will  give  135  pounds  terminal  pressure. 

40  "  "  180 

60  "  "  260  " 

80  '•  "  320 

This  method  of  testing  is  very  convenient  for  boiler-shop 
use,  as  the  device  is  small  and  compact,  easily  applied,  and 
requires  little  skill  to  operate.  Safety  valves,  which  usually 
form  part  of  the  apparatus,  may  be  set  for  any  desired  press- 
ure up  to  the  limits  of  the  instrument,  so  that  there  may 
be  no  danger  of  subjecting  the  boiler  to  excessive  strain. 
The  feed  supply  should  flow  under  an  unvarying  head  so 
that  the  conditions  under  which  the  jet  operates  may  remain 
constant,  and  rather  higher  counter  pressures  are  given  when 
the  water  is  received  under  a  head  than  when  it  is  lifted. 

The  suggestion  has  also  been  made  to  apply  the  power  of 
the  injector  for  increasing  available  pressure,  to  use  in  a 


APPLICATIONS  OF  THE*  INJECTOR.  123 

hydraulic  press,  but  it  is  doubtful  if  this  would  ever  be  of 
much  practical  value.  By  properly  proportioning  the  piston 
areas  of  the  press,  an  injector  could  be  substituted  for  the 
pumps  usually  employed,  but  practical  considerations  would 
at  once  suggest  themselves  which  would  render  the  supe- 
riority of  the  injector  exceedingly  dubious. 

For  fire  pumps  there  is  a  field     FrG  FJRE 

that  is  more  promising.  Small 
instruments  are  constructed  hav- 
ing steam  nozzles  about  the  same 
size  as  the  delivery  tubes,  and  are 
frequently  attached  to  yard  and 
switching  locomotives  with  good 
results ;  one  of  the_  most  promi- 
nent railroads  in  this  country  has 
supplied  its  yard  engines  with 
pumps  of  this  kind,  which  are 
operated  by  simply  opening  the 
tank  valve  and  the  steam  valve, 
and  coupling  up  a  line  of  hose. 
Fig.  37  gives  an  exterior  view  of 
this  style  of  fire  pump  which 
will  throw  4600  gallons  of  water 
per  hour  through  a  -J^-  fire  nozzle 
a  distance  of  115  feet.  It  can  be 
coupled  to  an  ordinary  fire  hyd- 
rant in  case  the  supply  of  water 
in  the  tank  is  insufficient.  The 
capacity  and  distance  given  are 
based  upon  a  steam  pressure  of 
125  pounds  per  square  inch. 

For  draining  or  raising  large 
quantities  of  water  a  small  height,  ejectors  can  be  used  with 
a  comparatively  small  expenditure  of  steam,  although  with 
considerable  less  economy  than  if  a  pump  wrere  used,  and 
there  are  but  few  cases  where  the  increase  in  temperature — 
the  chief  source  of  economy  in  the  injector  as  a  boiler  feeder 
— would  be  advantageous.  The  advantage  of  steam  con- 


124  THE   GIFFARD   INJECTOR. 

densation  is  of  use  indirectly  in  the  case  of  bilge  pumps, 
which,  beside  performing  the  function  for  which  they  are 
designed,  are  often  operated  when  the  engines  of  steamers 
are  stopped  at  sea  as  condensers  for  the  sudden  accumula- 
tion of  steam  until  the  fires  can  be  properly  checked.  These 
pumps  are  simply  constructed,  and,  having  no  valves,  are 
not  liable  to  stoppage. 

The  proportions  of  the  parts  of  an  ejector  vary  somewhat 
with  steam  and  counter  pressure  and  the  purpose  for  which 
it  is  to  be  used ;  the  ratio  of  the  area  of  the  steam  orifice  to 
the  delivery  tube  may  vary  from  0.25  to  i.oo,  to  0.8  to  i.oo, 
the  former  giving  a  strong  suction  in  a  well-shaped  tube  at 
the  higher  steam  pressures. 

As  exhaust  steam  condensers  for  reducing  the  back  pres- 
sure upon  the  piston  of  an  engine,  special  forms  have  been 
designed,  which  are  complete  in  every  detail  for  regulating 
the  water  supply  for  varying  loads,  and  large  numbers  are 
now  in  use.  The  arrangement  is  compact  and  reliable,  re- 
quires no  air-pump,  and  is  usually  less  expensive  than  the 
other  systems. 

There  are  numerous  other  devices  in  which  jets  of  steam 
are  used  for  moving  and  forcing  air  or  other  gases,  such  as 
exhausters,  blowers,  ventilators,  etc.;  but  as  they  do  not 
depend  upon  the  condensation  of  the  steam  which  is  in 
reality  the  inherent  characteristic  of  the  injector,  they  do 
not  come  within  scope  of  these  pages. 


CHAPTER  IX. 

DETERMINATION  OF  SIZE — INJECTOR  TESTS  —  DIAGRAMS  OF 

RESULTS. 

As  has  already  been  shown,  the  maximum  capacity  of  an 
injector  depends  upon  three  factors:  Steam  pressure,  height 
of  lift,  and  temperature  of  feed  water.  It  is  upon  the 
design  of  the  tubes  and  the  special  type  of  the  instrument 
that  the  extent  of  the  variation  depends  when  any  two  con- 
ditions are  given  and  the  third  altered.  This  has  been 
illustrated  by  the  approximate  formula,  No.  23,  on  page 
79,  which  shows  the  rise  in  capacity  with  the  pressure;  by 
Table  VII,  page  78,  where  the  steam  pressure  and  the  lift 
remained  constant,  and  the  feed  temperature  varied;  and 
Table  V,  page  76,  where  the  pressure  and  temperature  were 
constant,  and  the  height  of  lift  increased.  Two  diagrams, 
Figs.  39  and  40,  indicate  graphically  the  first  and  second 
cases  more  clearly  than  can  be  done  by  tabulation,  showing 
the  general  rules  that  hold  true,  though  in  a  varying  degree, 
for  all  styles  and  patterns  of  injectors.  It  is  thus  seen  that 
judgment — or,  preferably,  experiment — must  be  used  to  de- 
termine the  capacity  of  an  injector  for  any  conditions  differ- 
ing from  the  usual  practice,  and  a  full  statement  of  the  con- 
ditions should  be  submitted  to  a  competent  manufacturer 
whose  wider  experience  will  enable  him  to  give  accurate 
information. 

For  each  given  feed  temperature  and  height  of  lift  there 
is  a  limiting  steam  pressure,  beyond  which  there  is  no  fur- 
ther increase  in  the  capacity ;  this  limit  of  pressure  is  lower 
with  injectors  designed  for  stationary  boilers  than  those  used 
in  locomotive  sendee,  and  it  is  usually  a  function  of  the  inlet 
area  to  the  combining  tube,  and  varies  with  the  pattern  of 

125 


126  THE   GIFFARD  INJECTOR. 

injector;  considering  these  things,  it  is  always  better  before 
deciding  on  the  size  required  to  submit  the  following  data 
to  the  manufacturer : 

(a)  Required  capacity  in  cubic  feet  per  hour, 

(b)  Steam  pressure, 

(c)  Height  of  lift, 

(d )  Temperature  of  feed  water. 

Stating,  also,  any  special  conditions,  such  as  length  of  suc- 
tion pipe,  if  unusual,  or  an  excess  of  back  pressure,  often 
required  when  feeding  through  a  heater.  Some  forms  of 
injectors  are  so  designed  that  all  ordinary  conditions  of  ser- 
vice are  satisfactorily  covered  by  the  usual  form  supplied; 
but  others  require  slight  modifications  of  the  forms  of  tubes 
which  enable  them  to  operate  more  effectively  in  special 
cases. 

The  first  information  to  obtain  is  the  maximum  evapora- 
tion of  the  boiler ;  formerly  the  allowance  granted  per  nomi- 
nal horse  power  was  one  cubic  foot  of  water;  but  with  the 
great  advance  that  has  been  made  in  the  economy  of  the 
modern  stationary  engine,  about  one-half  that  amount,  or 
35  pounds  per  horse  power,  is  usually  regarded  as  sufficient. 
It  is  always  more  advisable  to  obtain  the  actual  evaporation, 
but  when  unknown  or  doubtful,  the  requirements  may  be 
obtained  from  the  estimated  steam  consumption  of  the 
engine,  calculated  from  an  indicator  card,  allowing  sufficient 
margin  for  other  drains  upon  the  steam  supply.  If  this  can- 
not be  done,  the  approximate  rules  here  given  can  be  used : 

To  FIND  WEIGHT  OF  WATER  EVAPORATED  PER  HOUR  <=  X] 

FROM   AND   AT   212°. 

When  the  heating  surface  (=  H)  is  known  : 

For  tubular  boilers,  X  =  H  X  3-4Q 
"    flue  "       X^HX  6.00 

Water  tube        "        X  =  H  X  3.5. 
When  the  grate  surface  (=  G)  is  known  : 

For  externally  fired  boilers,  X  —  G  X     94.00. 
"    internally  "  X  =  G  X  180.00. 

When  the  total  weight  of  combustible  burned  per  hour  (—  C)  is 
known  : 

X=  C  X  9-00,     (Assumed  as  a  fair  average.) 


SIZES   OF  INJECTORS. 


127 


When  the  heating  surface  (//)  and  grate  surface  (<7)  are  known  : 
For  internally  fired  boilers,  X  =  36.0  V  H  X  k1.' 

(Molesworth  Pocket  Book.) 

When  the  heating  surface  (//")  and  weight  of  combustible  (C)  are 
known  : 


A': 


(12-  4. 


375  X  -77   )   X  C 


NOTE.  —  To  reduce  weight  of  water  evaporated  from  and  at  212°  to 
the  corresponding  evaporation  from  a  feed  temperature  of  70°  and  a 
steam  pressure  of  70  pounds,  divide  by  1.183. 

To  find  weight  of  combustible,  subtract  from  total  weight  of  coal 
burned  per  hour,  the  weight  of  the  ashes  and  the  contained  moisture^ 

In  determining  the  size  of  injector  required  for  a  locomo- 
tive, the  size  of  the  cylinder  is  usually  taken  as  the  stand- 
ard, although  the  diameter  of  the  boiler,  and  the  special 
service  for  which  the  locomotive  is  intended,  has  a  modify- 
ing influence.  The  following  table  embodies  the  practice  of 
the  Baldwin  Locomotive  Works  for  all  engines  equipped 
with  two  injectors,  one  injector  and  one  pump,  one  injector 
and  two  pumps-, 

TABLE  IX. 

SIZES  OF  INJECTORS  FOR  LOCOMOTIVES. 


Diameter 
of 
Cylinders. 

Inches. 

Nominal  Size  of  Injector. 

Diameter 
of 
Cylinders. 

Inches. 

Nominal  Size  of  Injector. 

2  Injectors, 
or 
i  Pump  and 
i  Injector. 

2  Pumps 
and 
i  Injector. 

2  Injectors, 
or 
i  Pump  and 
i  Injector. 

2  Pumps 
and 
i  Injector. 

6,7,8 
9,  10 

I1,   I2,    13 

14,  15 

1  6,  17 

18 

3 
4 

8 

3 
3 
4 
4 
5 
6 

!         '9 

20 
21 
22 

23 
24 

8* 
9 

9* 

10 
10 

II 

6 
6 

*  Use  next  size  larger  with  specially  large  boilers. 

Almost  all  of  the  best  known  patterns  of  locomotive  injec- 
tors of  the  same  nominal  size  correspond  closely  in  maximum 
capacity,  even  though  the  weight  of  steam  used  per  hour 
will  vary  according  to  the  proportion  of  the  nozzles  and  the 
general  excellence  of  the  design.  With  injectors  for  station- 


128  THE  GIFFARD  INJECTOR. 

ary  boilers  there  is  less  uniformity,  and  no  general  standard 
prevails. 

With  instruments  purchased  from  reputable  manufac- 
turers, there  is  but  little  danger  of  the  capacity  falling  below 
the  figures  claimed  if  the  injector  is  operated  under  the 
conditions  prescribed  in  the  catalogue ;  owing  to  the  present 
refined  methods  of  duplication  of  parts,  nozzles  can  be  bored, 
reamed  and  turned  with  mathematical  accuracy  and  endless 
repetition,  so  that  there  is  no  excuse  for  poor  workmanship 
or  any  deviation  from  proper  dimensions ;  but  there  may  be 
flaws  or  spongy  places  in  the  main  castings,  and  these  defects 
do  not  always  become  apparent  until  after  the  injector  has 
been  subjected  to  the  vibration  of  an  engine,  escaping  detec- 
tion even  in  the  proving  room  of  the  manufacturer.  If  an 
imperfection  of  this  kind  should  occur  in  one  of  the  walls 
separating  the  steam  from  the  feed  chambers,  a  useless  heat- 
ing of  the  feed  water  would  result,  and  both  the  maximum 
capacity  and  the  highest  admissible  temperature  of  the  feed 
water  would  be  reduced.  Assuming  the  injector  to  be  in 
perfect  condition,  there  may  be  a  very  serious  falling  off  in 
the  capacity  below  that  claimed,  if  the  steam  pressure  or 
the  height  of  lift  during  the  test  are  greater  than  those  used 
by  the  makers ;  for  instance,  if  the  standard  were  based  upon 
a  pressure  of  120  pounds  per  square  inch  and  a  lift  of  i  foot, 
the  capacity  (based  upon  an  actual  case)  might  fall  off  10 
per  cent,  when  the  lift  is  increased  to  6  feet,  and  25  per  cent, 
when  the  steam  pressure  is  raised  to  150  pounds. 

These  considerations  show  the  advantage,  and,  in  some 
cases,  the  necessity  of  having  a  thoroughly-equipped  testing 
department  wherever  large  numbers  of  injectors  are  in  use, 
both  for  the  purpose  of  experiment,  but  more  especially  for 
proving  those  that  have  been  repaired  by  the  employee  in 
charge  of  this  work.  The  exact  conditions  occurring  in 
practice — steam  pressure,  height  of  lift  and  length  of  suction 
pipe — should  be  imitated  as  nearly  as  possible.  By  this  S}^- 
tem  the  performance  of  all  injectors  submitted  may  be  care- 
fully determined  without  premature  acceptance  of  manufac- 
turers' claims.  Many  of  the  large  railroad  companies  have 


SIZES  OF  INJECTORS. 


129 


appreciated  these  facts,  and  installed  in  their  laboratories 
apparatus  for  testing  new  forms  of  injectors,  as  well  as  to 
prove  one  or  two  selected  from  all  lots  submitted  for  regular 
service,  which  must  conform  to  the  standard  required  by  the 
railroad. 

The  standard  dimensions  to  which  all  injectors  used  on 
the  Pennsylvania  Railroad  are  required  to  conform  are  shown 
in  Fig.  38.  and  cover  chiefly  the  position  of  the  steam,  feed 
and  suction  pipes,  and  the  attaching  bolt,  so  that  all  pat- 
terns of  injectors  may  be  interchangeable.  As  these  pro- 
portions are  known  as  the  P.  R.  R.  Standard,  and  are 
used  by  several  of  the  large  companies,  a  list  of  the  prin- 
cipal dimensions  is  given  in  the  table  accompanying 

Fig.  38. 

FIG.  38, 


Nominal  Size  of  Injector. 

A 

B 

c 

D 

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No.  6  

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2£ 

2|1 

21 

No   7  

7i 

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2U 

2J- 

No   8  .  '.    .    . 

si 

IA.% 

21- 

3-* 

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No   9  ... 

Si 

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s 

2l 

Regarding  the  method  of  testing,  it  may  be  said  that  the 
simplest  way  is  to  empty  a  tank  of  known  dimensions  between 
given  levels,  delivering  against  a  check  or  lever  valve  loaded 


130  THE  GIFPARD  INJECTOR. 

to  the  initial  steam  pressure.  A  better  method  is  to  weigh 
the  feed  water,  and  if  possible,  the  delivery  also,  so  that  the 
weight  of  steam  used  per  hour  can  be  determined;  with 
small  injectors  this  can  almost  always  be  easily  done,  but 
with  locomotive  sizes  it  is  hardly  practicable  to  weigh  even 
the  feed.  From  an  experimental  point  of  view  it  is  interest- 
ing to  have  both  weights,  but  the  proportion  of  water  to 
steam  can  be  easily  determined  by  observing  the  feed  and 
delivery  temperatures,  and  applying  formula  (33)  given  on 
page  83,  which  is  sufficiently  accurate  for  all  ordinary  pur- 
poses ;  the  measuring  of  the  temperatures  is  best  done  by 
inserting  the  thermometer  bulbs  directly  in  the  flow  of  the 
water,  screwing  the  body  through  a  tee  having  a  3^  gas  pipe 
thread ;  special  instruments  are  made  for  this  purpose,  and 
are  more  satisfactory  than  the  inserted  mercury  cup.  The 
use  of  a  spring  check  valve  in  the  delivery  pipe  is  seldom 
satisfactory,  and  does  not  give  as  accurate  results  as  dis- 
charging directly  into  the  boiler,  or,  what  is  more  practica- 
ble, delivering  into  a  steam  trap  having  a  large  balanced 
outlet  valve,  and  connected  to  the  steam  area  of  the  boiler. 
This  arrangement  is  decidedly  the  best,  as  it  does  not  alter 
the  level  of  the  water  in  the  boiler,  and  the  pressure  against 
which  the  injector  delivers  is  maintained  constant,  giving 
more  precise  results  when  the  minimum  capacity  and  the 
highest  admissible  temperature  of  feed  water  are  to  be  deter- 
mined. 

The  most  convenient  and  instructive  method  of  recording 
comparative  tests  is  to  plot  the  results  in  the  form  of  the 
diagrams  given  in  Figs.  39  and  40.  Here  are  shown  tests 
of  three  of  the  best  known  locomotive  injectors  in  this  coun- 
try, the  object  being  to  ascertain  the  increase  in  capacity 
with  the  steam  pressure,  and  the  eifect  of  high  feed  temper- 
atures upon  the  maximum  and  the  minimum  capacities.  In 
both  diagrams  the  lines  parallel  with  the  base  line  represent 
gallons  per  hour ;  those  at  right  angles  indicate  steam  pres- 
sure in  Fig.  39>  and  feed  temperature  in  Fig.  40. 

These  series  of  tests  were  made  in  the  laboratories  of  two  of 
the  large  railroad  companies  at  considerable  time  and  expense, 


FIG.  39- 

COMPARATIVE  TESTS  OF  THE  MAXIMUM  AND  MINIMUM 
CAPACITIES  OF  THREE  PATTERNS  OF  No.  9  INJECTORS 
AT  VARIOUS  STEAM  PRESSURES.  Feed,  74° ;  lift,  6  feet. 


2800 
£700 
2600 
2500 
2400 


*2200 


ooo 

1500 

3  1800 

fc    , 

1700 

^1600 

^1500 

'"1400 


1200 

§1100 
> 
1000 

900 


800 


* 


40 


60 


80 

re  -^  -sure 


100 


120 


140 


MO 


131 


.132  THE  GIFFARD  INJECTOR. 

and  are  entirely  unbiased ;  yet,  in  order  to  avoid  any  com- 
parison of  the  relative  merits  of  the  different  patterns,  they 
are  here  indicated  alphabetically,  the  same  letters  applying 
to  similar  injectors  in  both  diagrams,  even  though  the  sizes 
are  different.  The  maximum  capacities  are  designated  by 
capital  letters,  and  the  minima  by  small  letters.  The  injector 
marked  O  is  not  the  same  pattern  as  the  C  shown  in  Fig. 
39;  but  as  it  is  the  product  of  the  same  manufacturer,  and 
has  similar  characteristics,  it  was  added  to  the  diagram. 

The  capacities  in  Fig.  39  were  obtained  by  noting  the  time 
required  to  deliver  a  measured  weight  of  water  against  a 
spring  check  valve.  The  lines  connecting  the  observations 
should  form  symmetrical  curves,  and  all  irregularities  indi- 
cate possible  errors  of  adjustment  or  of  observation  which 
are  difficult  to  detect  unless  the  results  are  plotted;  some 
patterns  of  injectors  require  very  careful  adjustment  of  both 
water  and  steam,  and  slight  variations  in  the  regulation 
materially  affect  the  result.  The  two  lines,  A  and  C,  keep 
rather  close  together,  while  B  delivers  more  water  at  the 
lower  pressures,  and  less  beyond  120  pounds,  at  which  pres- 
sure it  reaches  its  maximum.  A  apparently  starts  down- 
ward between  120  and  140  pounds  and  then  ascends,  indi- 
cating imperfect  regulation  at  the  reentrant  angle.  Referring 
to  the  minima,  the  lines  a  and  b  almost  coincide,  while  c 
gives  a  much  better  minimum  until  160  pounds  is  reached, 
when  the  sudden  rise  indicates  insufficient  throttling  of  the 
feed  valve.  If  the  steam  pressure  were  raised  still  higher,  a 
point  would  be  found  where  the  converging  lines  of  the 
maxima  and  minima  would  intersect,  which  would  be  at 
the  highest  steam  pressure  with  which  each  injector  can  be 
operated  under  these  conditions. 

In  the  tests  given  in  diagram,  Fig.  40,  the  steam  pressure 
and  the  height  of  lift  are  constant,  and  the  feed  temperature 
raised  5°  after  each  observation  until  the  injector  broke. 
This  was  done  to  obtain  under  each  condition  the  maximum 
and  the  minimum  capacity  of  each  injector;  the  latter  lines 
have  numerous  reentrant  angles,  due  to  the  fixed  notches 
which  the  regulating  mechanism  necessitated.  In  all  cases 


TESTS. 


133 


134  THE  GIFFARD  INJECTOR. 

the  two  capacities  should  be  identical  at  the  breaking  and 
overflowing  temperatures ;  this  is  true  with  lines  A  and  Ct 
and  probably  with  B  also,  if  prolonged  to  94°.  The  termi- 
nation of  each  line  indicates  the  highest  admissible  temper- 
ature of  the  feed  water  for  each  pattern  of  injector,  A 
breaking  at  110°,  B  at  90°,  and  Cat  125°. 

A  rather  curious  feature  of  the  tests  with  the  Cl  cl  injector 
is  the  crossing  of  the  two  lines,  showing  an  apparent  para- 
dox, that  the  minimum  capacity  at  115°  is  higher  than  the 
maximum.  In  this  pattern  the  regulation  was  obtained  by 
reducing  the  steam  supply,  and  as  it  is  well  known  that 
with  high  pressures  and  temperatures  a  smaller  steam  nozzle 
can  be  used  to  advantage,  it  follows  that  here,  where  the 
steam  area  is  reduced,  the  capacity  is  larger  than  when  the 
full  steam  nozzle  is  used,  but  which,  when  fully  opened, 
gives  best  results  at  lower  temperatures. 

By  contrasting  these  results,  will  be  seen  the  difficulty  of 
obtaining  a  formula  which  will  cover  accurately  all  the  con- 
ditions that  enter  into  the  performance  of  an  injector,  as  the 
actual  construction  exercises  such  a  modifying  influence 
upon  the  results.  The  equations  which  were  given  were 
based  upon  the  form  which  seemed  to  approximate  the 
theoretical  results,  which  would  of  course  be  a  self-adjusting 
injector  able  to  preserve  the  condition  of  the  jet  at  the 
instant  of  approaching  the  smallest  diameter  of  the  delivery 
tube  nearly  at  a  density  of  unity.  In  all  experimental  work 
upon  which  theoretical  conclusions  are  to  be  based,  great 
care  should  be  exercised  to  secure  accurate  observations, 
and  these  should  at  once  be  plotted  in  the  manner  shown, 
so  that  all  doubtful  results  can  be  checked,  and,  if  neces- 
sary, repeated. 

A  more  recent  test  than  those  already  described,  and  one 
in  which  special  precaution  was  taken  to  insure  accuracy, 
will  now  be  given ;  this  test  *  was  made  by  disinterested 
experts  with  apparatus  that  can  be  duplicated  in  almost  any 
railroad  shop  with  but  little*  preparation.  Any  official  de- 
siring to  make  a  comparative  test  of  the  injectors  in  use  on 
his  line,  can  apply  the  method  outlined  with  satisfactory 

*  Reprinted  by  permission  from  the  Railroad  Gazette. 


TESTS. 


135 


and  decisive  results  at  comparatively  small  expenditure. 
The  injector  used  in  this  test  was  a  No.  ioJ/2  of  the  Im- 
proved Sellers  1887  pattern,  and  it  was  chosen  in  common  with 
several  other  well-known  injectors  for  the  purpose  of  making 
a  selection  for  the  equipment  of  a  large  number  of  locomotives, 
and  to  ascertain  if  the  performance  at  certain  given  steam 
pressures  fulfilled  the  requirements  of  the  specifications. 

FIG.  42. 


Apparatus. — The  injector  (see  page  104)  was  supplied  with 
dry  steam  from  a  200  H.  P.  Babcock  and  Wilcox  boiler, 
through  a  3  in.  pipe  carefully  lagged  with  asbestos  covering. 
The  injector  was  bolted  against  the  side- wall  of  the  boiler 
with  the  starting  lever  and  water  supply  valve  within  con- 
venient reach  of  the  operator.  The  water  supply  was  main- 
tained at  a  constant  level  in  a  large  barrel  directly  below  the 
injector,  into  which  the  suction  pipe  was  extended  to  within 


136  THE   GIFFARD  INJECTOR. 

one  foot  of  the  bottom ;  this  pipe  was  2^  in.  diameter  up 
to  the  nipple  of  the  injector,  where  it  was  reduced  to  2  in. 

The  water  supply  was  weighed  and  delivered  into  the  suc- 
tion barrel  as  follows  :  Ten  feet  above  the  level  of  the  suction 
barrel  were  two  large  tanks,  forming  a  reservoir  capable  of 
holding  about  noo  gals.  From  the  3^  in.  flanged  pipe 
bolted  to  the  bottom  of  each  was  a  vertical  3  in.  pipe  extending 
into  the  suction  barrel,  6  in.  below  the  4  ft.  level ;  this  pipe 
was  made  amply  large,  so  that  under  the  head  available  the 
tanks  would  be  drained  and  the  pipe  emptied  before  the  level 
of  the  water  in  the  barrel  could  be  lowered  by  the  injector 
more  than  6  in.;  owing  to  the  slope  of  the  bottom  of  the 
tanks  and  the  large  size  of  the  emptying  pipe,  this  was  accom- 
plished without  the  slightest  trouble.  A  globe  valve  was 
placed  in  this  pipe  close  to  the  injector,  so  that  the  proper 
level  of  the  water  in  the  suction  barrel  could  be  maintained 
by  the  operator.  (See  Fig.  42.) 

Above  and  resting  on  these  water  tanks  was  a  500  Ib.  plat- 
form scale  carrying  a  47  gal.  barrel,  into  the  bottom  of  which 
was  screwed  a  2  in.  outlet  pipe  for  emptying  it  quickly  into 
the  iron  tanks  below  ;  this  pipe  was  kept  clear  of  the  sides  of 
the  tank  and  the  scale.  Another  pipe  brought  the  water  sup- 
ply from  the  city  mains  above  the  top  of  the  barrel,  and  as  it 
was  supplied  with  a  quick  acting,  tight  gate  valve,  the  barrel 
could  be  quickly  weighed  empty,  filled,  re-weighed  and 
emptied  into  the  iron  tanks  until  the  quantity  of  water  re- 
quired for  a  run  of  from  15  to  20  minutes  was  obtained. 

Additional  means  for  supplying  the  barrel  with  water  during 
the  preliminary  run  before  each  experiment  was  found  to  be 
necessary,  because  when  the  reservoir  was  filled  with  weighed 
water,  none  could  be  withdrawn  until  the  moment  the  exper- 
iment commenced.  For  this  purpose  a  2  in.  hose  was  run 
into  the  barrel  and  a  valve  placed  near  the  discharge  end, 
and  the  water  level  maintained  constant  until  all  prepara- 
tions were  completed  ;  this  valve  was  closed  and  hose  with- 
drawn before  the  valve  for  the.  reservoir  tanks  was  opened. 

Gauges  were  placed  so  that  the  pressure  in  the  steam  pipe 
or  in  the  delivery  pipe  could  be  obtained  alternately  on  either 


TESTS. 


137 


FIG.  43.    ARRANGEMENT  OF  PIPING  AND  GAUGES  FOR 
TESTING  INJECTORS. 


These  sires  of ftpes  would 
do  for  an  &'  ,.">  -9     .  mjectar. 


138 


THE  GIFFARD  INJECTOR. 


or  both  gauges,  or  simultaneously  on  separate  gauges ;  this 
arrangement  worked  very  satisfactorily,  and  the  admission 
of  any  error  due  to  the  difference  between  the  steam  and  de- 
livery pressures,  or  to  a  discrepancy  between  the  two  gauges, 
could  be  prevented.  Fig.  43  shows  the  arrangement  of 
pipes,  valves  and  gauges  by  which  this  was  accomplished, 
and  is  self-explanatory. 

As  the  delivery  of  the  injector  was  too  great  to  be  taken 
into  the  boiler  without  affecting  the  steam  pressure  carried, 
it  was  passed  through  a  special  balanced  valve  (Fig.  44), 
which  maintained  a  constant  pressure  equal  to  that  of  the 
boiler.  The  delivery  pipe  of  the  injector  was  coupled  to  the 
under  side  of  a  check  valve,  which  was  connected  to  a  piston 

FIG.  44. 


of  the  same  area,  upon  the  upper  side  of  which  full  boiler 
pressure  was  obtained  by  a  pipe  tapped  into  the  steam  supply. 

Measuring  Devices. — The  steam  gauges  had  been  sub- 
jected to  careful  test  and  calibration  by  the  makers;  at  the 
same  pressures  the  readings  of  the  two  gauges  agreed 
exactly. 

The  thermometers  were  tested  in  oil  every  five  degrees, 
both  up  and  down,  and  the  corrections  noted,  from  which  a 
table  was  made  and  used  to  obtain  actual  temperatures. 
The  delivery  thermometer  was  brass  cased,  and  was  screwed 
into  the  delivery  pipe  close  to  the  injector,  with  the  bulb 
well  immersed  in  the  passing  water ;  the  scale  was  divided 
to  single  degrees,  and  could  be  read  easily  to  half  degrees. 
It  was  corrected  for  the  error  due  to  the  compression  of  the 
bulb,  as  it  was  subjected  to  the  pressure  of  the  delivery. 


TESTS.  139 

The  scale  used  for  weighing  the  feed  water  was  tested  by 
United  States  standard  weights  and  found  to  be  correct.  The 
barrel  resting  upon  the  scale  platform  was  weighed  before 
and  after  each  filling,  so  that  the  exact  net  weight  of  water 
passing  into  the  receiving  tanks  each  time  could  be  deter- 
mined. 

The  filling  of  the  water  tank  reservoir  required  two  ob- 
servers, one  to  open  and  close  the  inlet  valve  from  the  city 
mains  and  the  valve  from  the  bottom  of  barrel  leading  into 
the  reservoir,  and  the  second  to  shift  the  tare  weight  for  the 
empty  and  the  full  barrel,  and  to  record  the  weights  upon 
suitably  prepared  blanks.  As  the  scale  registered  to  ^  lb., 
the  possible  error  was  very  small,  for  a  test  by  United  States 
standard  100  lb.  weights  after  the  experiment  was  completed, 
showed  no  change, 

Method  of  Testing. — The  reservoir  tank  having  been  filled 
with  the  required  weight  of  water,  the  valves  in  the  steam 
pipe  were  opened  wide,  and  the  water  drained  out ;  the 
water  regulating  valve  on  the  injector  was  opened  and  the 
cam  lever  over  the  waste  valve  was  set  so  as  to  allow  this 
valve  to  open  freely.  Precaution  was  taken  to  insure  the 
water  supply  being  free  from  dirt  and  chips  and  the  suction 
barrel  clean.  The  2  in.  hose  from  the  water  main  was  led 
into  the  barrel  and  the  injector  started  against  full  back 
pressure.  The  hose  discharged  beneath  the  surface  of  the 
water  to  prevent  air  being  carried  down  into  the  water  and 
interfering  with  the  free  flow  in  the  suction  pipe.  Obser- 
vations were  made  as  to  the  regularity  of  the  steam  pressure, 
and  the  readings  of  the  steam  gauges  and  the  thermometers 
in  the  suction  barrel  and  delivrey  pipe  were  found  to  be  prac- 
tically constant ;  an  observer  was  stationed  at  the  water  valve 
in  the  3  in.  pipe  leading  from  the  overhead  reservoirs, 
another  to  read  the  gauges  and  thermometers,  and  a  third 
to  take  and  record  all  readings  and  note  the  general  perform- 
ance of  the  injector.  When  everything  was  ready,  the  barrel 
was  rapidly  filled  through  the  hose  and  then  its  valve  closed 
and  the  hose  entirely  withdrawn  ;  as  soon  as  the  water  level 
in  the  barrel  was  drawn  down  by  the  injector  to  the  lower 


140  THE  GIFFARD  INJECTOR. 

white  line  (b)  (see  Fig.  43),  the  recorder  noted  the  exact  time 
on  a  stop  watch,  the  other  observers  noted  the  thermometer 
and  gauge  readings,  while  the  valve  in  the  3  in.  feed  pipe 
from  the  reservoirs  was  quickly  opened  and  the  water  level 
raised  to  the  line  (a)  four  feet  below  the  centre  of  the  injector, 
where  it  was  maintained  during  the  continuation  of  the  ex- 
periment by  careful  regulation  of  the  valve.  Readings  of  the 
thermometers  and  the  gauges  were  taken  every  three  minutes 
until  the  reservoir  was  empty,  which  could  be  immediately 
noted  by  the  rapid  falling  of  the  level  of  the  water  in  the 
barrel ;  just  before  the  lower  level  was  reached  the  end  of  the 
3  inch  pipe  from  the  reservoir  was  exposed,  this  construction 
being  insisted  upon  so  that  the  observer  could  be  certain  that 
all  the  water  in  the  reservoir  had  flowed  into  the  barrel ; 
when  the  lower  level — from  which  the  start  was  made — was 
reached  the  signal  was  given  to  the  recorder,  and  the  time 
again  noted,  the  difference  in  time  being  that  required  to  lift 
and  force  against  initial  pressure  the  total  weight  of  water 
contained  in  the  reservoir  ;  from  this  could  be  calculated  the 
capacity  of  the  injector  in  pounds,  cubic  feet  or  gallons  per 
hour. 

The  method  of  determining  the  minimum  was  the  same, 
except  that  occasional  adjustment  of  the  regulating  valve 
was  required  during  the  experiment  owing  to  variations  in 
the  pressure  of  the  steam;  also,  the  quantity  of  water  weighed 
into  the  reservoir  was  less  than  half  that  used  for  determin- 
ing the  maximum.  Care  was  taken  that  the  counter  pres- 
sure produced  by  the  back-pressure  valve  should  always  be 
equal  to  that  of  the  boiler  so  as  to  obtain  precise  results. 

From  these  two  sets  of  experiments  were  determined  the 
figures  for  the  ratio  of  the  minimum  capacity  to  the  max- 
imum; subtracting  this  from  100  gives  the  "range"  in 
percentage  of  maximum. 

To  determine  the  relation  between  the  weights  of  the 
supply  water  and  of  the  steam  required  to  force  it  into  the 
boiler,  it  is  evident  that  the  simplest  method  would  be  to 
subtract  the  known  weight  of  the  supply  from  the  weight  of 
the  delivered  water  and  then  divide  the  weight  of  the  supply 


TESTS.  141 

by  this  difference.  With  small  injectors  this  is  often  done, 
as  the  volume  of  water  to  be  handled  is  not  large,  but  with 
an  instrument  of  the  size  used,  this  method  becomes  imprac- 
ticable. The  method  of  delivery  temperatures  was  therefore 
substituted  and  the  same  results  obtained  without  the  neces- 
sity for  weighing  the  delivery.  The  formula  used  was  the 
following  :  (See  page  83.) 


_ 


W=  Weight  of  water  delivered  per  pound  of  steam. 
H  =  Total  heat  in  one  pound  of  steam  (absolute)  pressure  above  32 

deg.  taken  from  steam  tables. 
T=  Temperature  of  the  delivered  \vater. 
t  =  Temperature  of  the  water  supply. 
/*—  Steam  pressure  (gauge). 

Maximum  water-supply  temperatures  were  obtained  by 
returning  some  of  the  water  from  the  delivery  pipe  to  the 
barrel  or  reservoir  ;  care  was  taken  that  the  hot  and  cold 
water  should  be  thoroughly  mixed  and  that  the  temperature 
should  not  be  increased  too  rapidly.  Two  sets  of  results  are 
given  :  limiting  temperatures  at  each  steam  pressure  for  auto- 
matic restarting  without  subsequent  waste  of  hot  water  or 
steam  from  the  overflow  ;  also  maximum  operating  tempera- 
ture at  which  the  injector  will  run  without  the  jet  breaking  ; 
the  former  were  obtained  with  the  waste  valve  free  to  rise 
on  its  seat;  the  latter,  with  the  waste  valve  closed  by 
throwing  the  cam  lever  backward  ;  in  this  case  if  the  jet 
breaks,  steam  will  flow  back  into  the  suction  pipe  until  the 
waste  valve  is  allowed  to  open  or  the  steam  supply  is  -shut  off. 

Numerous  special  tests  were  also  made  to  determine  the 
action  of  the  injector  under  conditions  frequently  occurring 
in  practice,  such  as  variations  of  the  steam  pressure,  hot 
water  in  suction  pipe,  and  the  effect  of  a  temporary  interrup- 
tion of  the  .water  supply,  such  as  would  occur  when  the 
movement  of  the  water  in  the  tank  of  a  locomotive  uncovered 
the  end  of  the  suction  feed  pipe  ;  also,  the  amount  of  water 


142  THE   GIFFARD  INJECTOR. 

wasted  during  starting  and  stopping.  An  account  of  these 
tests  will  be  made  under  the  heading  of  ' '  Results. ' ' 

It  should  be  noted  that  all  the  experiments  were  made 
without  throttling  the  steam  supply ;  this  was  found  to  be 
necessary  as  an  early  experiment  at  150  Ibs.  steam  showed 
that  the  superheating  due  to  wire  drawing  materially  affected 
the  results ;  in  all  subsequent  tests  the  pressure  of  the  boiler 
was  raised  or  lowered  to  meet  the  requirements  of  the  experi- 
ment. 

The  directions  given  in  the  catalogue  of  the  manufacturers 
for  stopping  and  starting  the  injector  were  followed:  To 
start :  Pull  out  the  lever.  To  stop  :  Push  in  the  lever.  Regu- 
late for  quantity  with  water  valve.  In  starting  on  high  lifts 
and  in  lifting  hot  water,  it  is  best  to  pull  the  lever  slowly. 

Results. — To  facilitate  the  comparison,  the  performance  of 
the  injector  at  different  pressures  and  the  results  obtained  at 
each  set  of  experiments  have  been  plotted  in  separate  dia- 
grams, forming  curved  or  broken  lines  connecting  the  several 
observations,  so  that  the  results  for  any  intermediate  condi- 
tion can  be  easily  determined ;  as  the  scale  of  the  diagrams  is 
necessarily  small,  a  complete  table  of  results  has  been  given, 
which  contains  the  actual  figures  obtained.  The  results  of 
the  tests  were  remarkably  good,  for  in  several  cases  the 
claims  of  the  manufacturers  were  much  exceeded.  Accom- 
panying each  diagram  is  a  short  review  of  the  results. 

As  stated  above,  however,  certain  tests  were  made  which 
could  not  be  tabulated,  but  are  almost  equally  valuable  in 
considering  the  general  performance  of  a  locomotive  boiler 
feeder. 

(A)  Variation  in  steam  pressure.  The  injector  was  started 
with  the  lever-starting  valve  and  the  water-regulating  valve 
wide  open,  and  the  pressure  in  the  boiler  and  the  back  pres- 
sure were  simultaneously  lowered  from  200  Ibs.  to  120  Ibs. 
and  then  later,  with  all  valves  as  before,  from  120  Ibs.  to  40 
Ibs.  steam,  without  a  drop  of  water  appearing  at  the  overflow; 
raising  the  same  pressure  caused  no  overflow  of  steam  or 
water  at  the  waste  pipe,  and  the  injector  seemed  to  operate 
as  successfully  at  one  pressure  as  another,  without  making 


TESTS.  143 

change  in  the  tubes  or  in  the  position  of  its  steam  or  water 
valve. 

(B)  From  the  fact  that  this   injector  worked  very  satis- 
factorily with  hot  supply  water,  it  was  evident  that  its  lift- 
ing power  with  the  suction  pipe  warm,  would  also  be  good ; 
owing  to  the  provision  of  large  overflows  in  the  forcing  com- 
bining tube,  it  is  not  necessary  that  care  should  be  used  in 
admitting  steam  to  the  main  jet  after  priming — as  is  the  case 
with  other  forms  of  injectors — for  even  though  the  feed  water 
be  above  the  limiting  temperature  as  it  comes  from  the  lift- 
ing nozzle,  the  forcing  jet  will  not  break,  but  will  cause  an 
overflow  of  steam  and  hot  water  until  the  hot  water  is  drawn 
out,  which  usually  occurs  in  a  few  seconds  ;  in  this  case  the 
amount  of  waste  was  small,  but  with  cold  water  only  a  few 
drops  appeared  at  the  waste  nozzle  at  60, 120,  200  Ibs.  of  steam 
or  intermediate  pressures.     The  mean  of  a  number  of  tests, 
stopping  and  starting  the  injector  with  the  supply  water  at 
ordinary  temperatures,  gave  one-half  pint    as   the  amount 
wasted  each  time. 

(C)  It  has  been  found  by  the  experimenters  that  the  effect  of 
admission  of  air  to  the  suction  pipe  of  all  injectors  which 
adjust  their  capacity  to  suit  variations  in  the  steam  pressure 
is  to  immediately  break  the  jet,  and  to  cause  the  steam  to 
blow  back  through   the  hose  into  the  tank ;  but  with  this 
instrument  any  such  interference  with  the  normal  condition 
of  the  jet  causes  a  waste  of  steam  or  water  at  the  overflow 
pipe,  which  ceases  as  soon  as  the  disturbing  cause  is  removed. 
To  test  this  feature,  the  water  in  the  suction  barrel  was 
allowed  to  fall  below  the  lower  end  of  the  suction  pipe,  so 
that  air  would  be  sucked  up  into  the  injector.     This  caused 
a  discharge  of  steam  and  air  from  the  waste  pipe,  which 
ceased  as  soon  as  the  usual  level  of  the  water  in  the  barrel 
was  restored.     This  test  was  repeated  at  200  Ibs.  steam  pres- 
sure, when  the  lifting  of  the  supply  water  and  the  forcing 
it  into  the  boiler  occurred  the  instant  the  water  covered  the 
end  of  the  suction  pipe. 

In  regard  to  the  injector  itself,  it  may  be  said  that  it  re- 
sponded promptly  at  all  times  to  the  movement  of  the  start- 


144 


THE  GIFFARD  INJECTOR. 


ing  valve.  It  is  started  and  stopped  by  the  continuous 
motion  of  a  single  lever,  and  was  regulated  by  a  side  motion 
of  the  quadrant  regulating  lever  only  for  the  purpose  of  alter- 
ing the  amount  of  delivery.  Its  construction  is  simple  and 
easily  understood  ;  no  outside  rods,  levers  or  bell- cranks  are 
used,  nor  complicated  internal  valves.  When  hot  water  is  to 
be  lifted  it  was  found  that  the  strongest  suction  was  obtained 
when  the  starting  lever  was  drawn  forward  about  i  in.  and 

FIG.  45- 


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the  remainder  of  the  stroke  given  after  water  appeared  at 
the  waste  pipe. 

The  Diagrams. — Fig.  No.  45  is  a  graphical  representation 
of  the  capacity  tests  given  in  lines  I  and  5  of  the  Table  of 
Results.  At  the  top,  ranging  from  left  to  right,  are  gauge 
pressures  in  pounds  per  square  inch,  from  30  to  200  Ibs.  ; 
the  horizontal  lines  indicate  gallons  of  water  taken  from  the 
supply  tank  per  hour,  so  that  the  heavy  curved  line  shows 


TESTS. 


145 


the  change  in  the  capacity  with  the  steam  pressure.  The 
maximum  capacity  increases  as  the  pressure  rises  from  1,912 
gals,  at  30  Ibs.  to  2,535  at  6o  IDS->  then  3,510  at  120,  3,760  at 
1 50  and  4, ooo  at  200  Ibs.  steam  ;  the  last  capacity  is  higher  than 
that  at  any  lower  steam  pressure,  and  was  above  that  of  any 
other  injector  of  the  same  size,  even  though  the  capacity 
may  be  the  same  at  120  or  150  Ibs.  The  minimum  is  shown 
by  the  lower  heavy  line  of  the  diagram,  and  increases  from 
765  gals,  at  30  Ibs.  to  1,732  at  200  Ibs.  steam ;  this  possible 
reduction  of  the  capacity  at  200  Ibs.,  from  4,005  gals,  to 
1,732,  is  such  a  great  variation  in  the  amount  of  water  deliv- 

FIG.  46. 


62 
60 

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to 

ered  that  it  is  very  evident  that  the  injector  can  be  used  to 
feed  the  boiler  continuously  with  either  a  light  or  heavy 
train. 

The  ratios  between  the  maximum  and  the  minimum  are 
given  by  the  heavy  line  in  the  lower  part  of  Fig.  No.  46, 
and  the  range  in  percentages  is  given  in  the  upper  part. 
These  same  values  are  given  in  lines  8  and  10  of  the  table. 

Upon  the  figures  obtained  during  the  test  to  determine  the 

maximum  capacity,  are  based  the  values  given  in  Fig.  47, 

page  146,  also  line  4  of  table,  which  show  the  weight  of  water 

taken  from  the  supply  tank  per  Ib.  of  steam  used  by  the 

10 


146 


THE   GIFFARD   INJECTOR. 


injector.  This  represents  the  actual  amount  of  mechanical 
work  done  by  the  steam,  and  is  a  point  of  special  value  to 
practical  men ;  it  is  a  good  gauge  of  the  efficiency  of  the 
design  of  the  injector  and  of  its  economy  as  a  boiler  feeder, 
as  it  indicates  that  the  minimum  amount  of  steam  is  used  to 
perform  the  work  of  feeding,  and  no  excess  is  condensed  and 
utilized  only  for  heating  the  feed  water.  Under  the  same 
conditions  of  supply  temperature  and  lift,  the  weight  of  water 

FIG.  47. 


26 
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950  60  70  GO  90  /OO      i20       /W      /6O       180      ZOO 
STEAM-  PfffSSUfffS 

delivered  per  pound  of  steam  must  always  decrease  as  the 
pressure  rises. 

A  critical  comparison  of  the  results  obtained  on  this  experi- 
ment proves  the  superior  design  of  this  pattern.  Referring 
to  the  actual  figures  of  Fig.  47  or  the  table,  it  is  seen  that 
at  120  Ibs.  steam,  13.6  Ibs.  of  water  are  taken  from  the 
tank  and  forced  into  the  boiler  by  i  Ib.  of  steam  and  at 
200  Ibs.  10.34  Ibs.,  the  latter  result  being  especially  remark- 
able. 


TESTS. 


147 


It  is  very  seldom  necessary  that  a  locomotive  injector  is 
required  to  feed  when  the  temperature  of  the  supply  exceeds 
loo  degs.,  but  when  the  occasion  demands,  the  action  should 
be  certain  and  permit  a  fair  range  of  capacities.  Many  in 
jectors  will  not  operate  at  the  higher  pressures  with  the  sup- 
ply at  this  temperature,  consequently  their  action  when  start- 
ing with  hot  feed  pipes  causes  a  very  large  amount  of  over- 
flow before  the  jet  enters  the  boiler.  Several  temperature 
tests  were  made  at  30,  60,  120  Ibs.  steam,  etc.,  and  the  results 
are  given  in  Fig.  No.  48  and  lines  n  and  12  of  table.  The 


FIG.  48. 


^ 


X5 


*«l 


30    4O   SO    6O     TO     QO    9O 


limiting  temperature  at  which  the  injector  is  re-started  at  va- 
rious steam  pressures  is  given  by  the  lower  line,  and  the  max- 
imum temperature  to  which  the  supply  may  be  raised  before 
the  injector  ceases  to  operate  is  shown  by  upper  line.  The 
vertical  lines  of  the  diagram  indicate  steam  pressures  as 
before  and  the  horizontal  lines  degrees  Fahrenheit.  Starting 
at  30  Ibs.  steam,  the  limiting  temperature  is  138  degs.,  which 
rises  to  143  degs.  at  60  Ibs.  ;  at  120  it  is  137  deg.,  and  at  150 
Ibs.  pressure  133  degs  These  were  obtained  with  the  waste 
valve  closed  to  prevent  the  waste  which  would  occur  as 
these  limiting  temperatures  were  approached. 


148 


THE  GIFFARD  INJECTOR. 


It  may  be  stated  that  the  greatest  care  was  taken  to  pre- 
vent the  possibility  of  error  in  observation  or  in  accuracy  of 
apparatus.  The  operators  were  all  skilled  in  experimental 
work  and  the  observation  and  calculation  of  each  were  care- 
fully checked.  The  injector  was  taken  directly  from  stock 
and  without  special  preparation,  and  in  performance  it  ex- 
ceeded in  every  detail  the  requirement  of  the  specification. 

TABLE  OF  RESULTS. 

Test  of  a   Sellers'  Improved    Injector   of  1887 ;    Size,  10^ ;    Lift,   4 
feet;  Supply  Water  Weighed. 

MAXIMUM   CAPACITY. 


I 

Mean  Steam  Pressure  

30 

60 

122 

151 

200.5 

Gallons  of  Water  per  Hour    .    . 

1912 

2535 

3517 

3765 

4005 
50.5 

2 

3 
4 

Temperature  of  Supply  Water  . 

67.0 

67.0 

54-0 

50.0 

Temp,  of  Delivered  Water  .    .    . 

"3-25 

125.0 

133-4 

135-7 

i54.o 

Weight  of  delivered  Water  per 
Pound  of  Steam  Used  .... 

25.90 

19.10 

13.60 

12.60 

IQ.34 

MINIMUM   CAPACITY. 


5 

Mean  Steam  Pressure   

30 

765 

60 

1  2O 

I48 

200.  6 

Gallons  of  Water  per  Hour     .    . 

937 

1290 

1432 

1732 

6 

Temperature  of  Supply  Water  . 

67.0 

67.0 

212 

54-5 

55.o 

50.0 

7 

Temp,  of  Delivered  Water     .    . 

171 

238 

250 

263 

RANGE). 


Mean  Steam  Pressure  

30 

60 

121 

'49-5 

8 

Per  cent.  Capacity  of  Max.     .    . 

40.0 

37.o 

36.6 

38.0 

9 

10 

Actual  Range  in  Gals,  per  Hour 

1147 

1598 

2227 

2333 

Per  cent.  Range  of  Max.  Capac'y 

60.0 

63.0 

63.3 

62.0 

200.5 
43-2 
2273 
56.8 


LIMITING  TEMPERATURE   OF  WATER  SUPPLY.      DEG.   FAHR. 


Mean  Steam  Pressure       .... 

3° 

60 

1  20 

150 

II 

12 

Limiting  Re-starting  Temp.    .    . 

130 

135 

122 

120 

Limiting  Operating  Temp.      .    . 

139 

144 

137 

133 

CHAPTER  X. 

REQUIREMENTS  OF  MODERN  RAILROAD  PRACTICE— REPAIRS 

AND   RENEWALS — METHODS   OF   FEEDING 

LOCOMOTIVE   BOILERS. 

Owing  to  the  introduction  of  the  compound  locomotive  or 
the  demand  for  motive  power  having  increased  hauling  capa- 
city, there  has  been  a  general  tendency  during  the  last  few 
years,  to  materially  increase  the  pressure  of  the  steam  carried 
on  locomotive  boilers,  and  almost  all  new  engines  are  de- 
signed to  carry  from  180  to  205  pounds  steam  pressure. 

The  designing  of  an  injector  for  these  high  pressures  is  a 
much  more  difficult  problem  than  was  before  presented.  The 
higher  the  operating  pressure,  the  greater  the  difficulty  in 
fulfilling  the  requirements  of  a  good  locomotive  injector.  The 
criticism  against  most  injectors,  and  a  characteristic  of  the 
single  jet,  fixed  nozzle  type,  is  that  if  it  is  proportioned  to 
operate  at  180  or  200  pounds  of  steam,  it  cannot  be  made  to 
work  at  the  low  pressures  carried  in  the  round  house.  There 
are  now  in  the  market  several  special  forms  of  injector, 
which  show  commendable  effort  to  meet  the  new  condi- 
tions, and  which  operate  over  a  wide  range  of  pressure.  All 
injectors  with  fixed  nozzles  are  most  efficient  at  the  special 
pressure  for  wrhich  the  tubes  are  designed,  and  although 
they  admit  by  hand  adjustment  of  considerable  variation  of  the 
steam  pressure,  yet  at  no  other  higher  pressure  will  they  ope- 
rate as  efficiently.  With  injectors  having  two  sets  of  tubes, 
this  permissible  range  is  much  more  extended,  but  the 
mechanical  efficiency  is  seldom  as  high  as  that  of  some  of 
the  special  types. 

But  the  principal  feature  which  interests  the  user  or  pur- 
chaser of  the  injector,  is  the  falling  off  in  the  capacity  as  the 
steam  pressure  is  raised,  which  often  necessitates  the  pur- 

149 


150  THE   GIFFARD  INJECTOR. 

chase  of  a  larger  size  instrument  to  obtain  the  required  num- 
ber of  gallons  per  hour.  This  entails  the  consumption  of 
more  steam,  with  a  heavier  drain  on  the  boiler  and  conse- 
quent loss  of  pressure.  Further,  the  action  at  these  pressures 
is  less  certain  and  the  jet  much  more  sensitive. 

Considering  the  problem  in  detail,  it  will  be  seen  that 
there  are  a  number  of  features  which  it  is  advantageous  that 
a  modern  locomotive  injector  should  possess,  and  which  are 
found  to  a  greater  or  less  extent  in  certain  of  the  most 
improved  types. 

One  of  the  chief  requirements  is  simplicity  of  construction 
and  operation  ;  special  care  should  not  be  required  to  prime, 
regulate  and  start ;  every  unnecessary  movement  of  the  engi- 
neer should  be  dispensed  with;  the  injector  should  be  ope- 
rated and  adjusted  by  the  movement  of  a  single  lever,  or  at 
most,  by  two,  one  for  the  steam  valve  and  the  other  for  the 
feed  supply.  The  action  should  be  positive,  so  that  when 
once  started,  it  can  be  depended  upon  to  operate  continu- 
ously without  being  affected  by  shock  or  jar,  or  change  of  level 
of  water  supply  ;  it  is  obvious  that  every  demand  upon  the 
attention  of  the  engineer  by  the  lubricator,  injector  or  other 
device  connected  with  the  engine,  requires  time  that  should 
be  devoted  to  the  operation  of  the  engine  itself,  watching 
the  track  for  passing  signals  or  adjusting  the  cut-off,  and 
therefore  each  device  should  be  as  nearly  self-operative  as 
possible. 

Fully  as  important  as  simplicity  of  construction,  is  the 
general  action.  A  locomotive  injector  should  operate  equally 
well  throughout  the  complete  range  of  boiler  pressures 
without  hand  adjustment  of  any  kind  Not  only  is  this 
necessary  on  the  road  for  the  reasons  outlined  above,  but  on 
account  of  the  use  of  the  injector  by  the  hostlers  or  men  in 
charge  of  the  engines  in  the  round  house.  It  should  give 
the  maximum  delivery  at  200  pounds  steam  and  work  with 
a  wide-open  lazy  cock  at  20  and  30  as  well  as  at  200  pounds, 
for  it  is  evident  from  the  discussion  of  the  theory  of  the 
injector,  that  the  capacity  should  vary  with  the  steam  pres- 
sure ;  now  if  it  is  necessary  to  regulate  the  water  supply 


REQUIREMENTS.  151 

when  the  pressure  falls,  for  instance,  from  180  to  160  pounds, 
due  to  a  special  drain  upon  the  steaming  capacity  of  the 
boiler,  the  attention  of  the  engineer  is  taken  from  his  other 
duties  and  must  regulate  and  adjust  his  feed,  to  prevent  all 
the  delivered  water  from  the  injector  passing  out  through 
the  overflow  into  the  ash  pan. 

It  is  very  desirable  also  to  have  a  wide  range  of 'capacities 
at  the  usual  working  pressure.  This  is  difficult  to  obtain  at 
1 80  and  200  pounds  steam,  but  in  order  to  obtain  the  best 
results  in  feeding,  the  range  should  be  at  least  50  per  cent., 
and  more  if  possible.  The  special  reasons  for  this  will  be 
given  in  connection  with  the  methods  of  feeding  locomotive 
boilers. 

On  page  65  is  given  the  difference  between  the  amount  of 
steam  used  by  two  different  styles  of  injectors  ;  this  is  due 
in  great  measure  to  the  use  of  a  larger  steam  nozzle  than  is 
necessanr.  An  injector,  is  practically  a  pump  in  which  the 
actuating  steam  is  condensed.  Treat  the  injector  as  a  me- 
chanical device ;  that  device  which  gives  the  required 
delivery  with  the  minimum  consumption  of  steam  or  energy, 
is  the  most  efficient.  Every  pound  of  steam  taken  out  of  the 
steam  space  means  a  subtraction  of  a  pound  of  steam  from 
use  on  the  pistons,  and  there  are  times  during  a  heavy  pull, 
when  steam  in  the  cylinders  is  much  more  valuable  than  hot 
water  in  the  boiler.  The  author  has  known  of  cases  where 
there  has  been  shown  a  very  material  improvement  in  the 
performance  of  a  badly  steaming  engine  by  changing  to  a 
more  economical  form  of  injector.  By  an  efficient  injector  is 
meant  one  in  which  the  delivery  is  large  per  unit  weight  of 
steam.  What  this  ratio  should  be,  is  difficult  to  say,  but 
recent  improvements  have  raised  the  delivery  of  water  per 
pound  of  steam,  from  8.8  pounds  to  11.2  at  180  pounds  pres- 
sure. Besides  the  advantage  of  having  less  tendency  to  pull 
down  the  steam  pressure,  an  efficient  injector  induces  a  certain 
amount  of  economy  in  the  coal  consumption,  by  increasing 
somewhat  the  evaporative  capacity  of  the  boiler.  The 
greater  the  difference  between  the  temperature  of  the  waste 
gases  passing  into  the  smoke-box  and  the  feed  water,  the 


152  THE   GIFFARD  INJECTOR. 

greater  the  transfer  of  heat  through  the  boiler  tubes  to  the 
water.  The  temperature  of  the  waste  gases  varies  from  800 
to  1200  degrees,  and  if  any  part  of  this  waste  heat  can  be 
absorbed  by  the  feed  water,  it  is  a  clear  gain,  and  this  can 
be  obtained  by  using  a  lower  temperature  of  the  delivery, 
with  smaller  steam  consumption. 

There  is  another  feature  which  commends  itself  to  many 
practical  railroad  men,  not  only  on  account  of  the  added 
certainty  given  to  the  action  of  a  locomotive  injector  under 
all  conditions,  but  for  the  convenience  in  obtaining  the  full 
range  of  capacities.  When  an  injector  is  re-starting,  it  will 
continue  to  force  water  into  the  boiler  as  long  as  it  is  sup- 
plied with  water  and  steam,  and  will  not  blow  steam  back  into 
the  suction  pipe  even  if  the  continuity  of  the  jet  should  be 
disturbed  by  an  interruption  of  the  water  or  steam  supply; 
further,  the  water  supply  can  be  reduced  below  the  actual 
minimum  capacity  of  the  injector  without  breaking  the  jet, 
so  that  close  regulation  can  be  obtained  without  special  care. 
Operating  closed  overflow  injectors  at  high  pressures  on  fast 
express  trains  is  avoided  by  engineers  wherever  possible,  if 
there  be  slightest  danger  of  the  injector  breaking,  for  the 
time  occupied  in  repriming  and  starting  an  injector  with  hot 
pipes  may  be  two  or  three  minutes,  sufficient  for  the  train 
to  have  covered  as  many  miles,  during  which  time  the  atten- 
tion of  the  engineer  must  be  more  fully  occupied  with  the 
injector  than  his  other  duties.  The  probability  is,  therefore, 
that  the  engineer  will  run  no  such  chance,  and  will  operate 
his  injector  with  the  least  risk  of  losing  time,  even  though 
his  method  of  feeding  the  boiler  may  not  be  the  best  for 
obtaining  economy  of  fuel. 

The  temperature  of  the  supply  water  does  not  often  enter 
into  the  consideration,  so  long  as  the  range  of  capacities  of 
a  locomotive  injector  is  not  affected  by  summer  temperatures. 
Some  of  the  South  American  and  foreign  railroads  specify 
the  limiting  temperature  of  the  water  supply,  but  these  cases 
are  exceptional ;  the  introduction  of  blow-back  valves  or  the 
return  of  the  air-brake  exhaust  to  the  tank  has  required  the 
use  of  hot-water  injectors  in  a  few  cases,  but  at  the  present 


REPAIRS.  153 

time  the  use  is  not  general,  for  it  is  generally  accepted  that 
no  uncertainty  should  be  allowed  in  the  feed  apparatus,  and 
any  increase  in  the  temperature  of  the  water  supply  renders 
the  action  of  any  injector  less  efficient  and  consequently 
reduces  the  length  of  life  of  the  tubes. 

REPAIRS. 

Given  an  injector  which  has  been  accepted  by  the  officials 
of  a  railroad  as  the  most  suitable,  the  next  practical  question 
which  arises  is  that  of  maintenance  and  repair.  If  it  fulfill  the 
first-named  requirement  of  simplicity  of  construction,  it  will 
not  be  difficult  for  the  employee  having  special  care  of  the 
boiler  feeders  to  comprehend  the  ordinary  cause  of  com- 
plaint on  the  part  of  the  engineer  or  fireman  who  operates  it. 
A  few  practical  hints  to  the  inspector  may  be  of  value. 

The  first  duty  on  his  part  will  be  to  examine  the  connec- 
tions and  joints  to  discover  leaks  or  stoppage  in  the  strainer, 
suction  and  delivery  pipe,  and  the  check  valves.  These 
proving  to  be  in  good  condition,  the  injector  should  be 
tested  under  full  working  pressure.  The  methods  then  to 
follow  depend  to  a  great  extent  upon  the  style  of  injector, 
and  its  action  during  this  test.  Assuming  it  to  be  of  the 
single-jet,  fixed-nozzle  class,  like  the  Monitor,  Ohio,  Mack, 
etc.,  and  that  it  cannot  be  made  to  prime,  the  fault  probably 
lies  with  the  lifting  spindle  or  priming  nozzles.  If  these 
nozzles  are  separate,  as  in  the  older  form  of  Monitor,  first 
examine  the  lifting  steam  nozzle  to  see  if  stopped  up,  then 
if  tightly  screwed  to  seat,  and  lastly,  joint  of  body,  as  air  may 
enter  the  combining  tube  at  this  place  and  so  destroy  the 
suction.  The  overflow  nozzle  may  be  bent,  loose  or  out  of 
line,  or  the  drip  pipe  so  close,  or  of  such  small  size,  that  the 
free  discharge  of  steam  is  impeded  ;  or  the  steam  valve  to 
the  main  steam  nozzle  may  leak  to  such  an  extent  as  to  fill 
the  suction  pipe  and  prevent  the  lifting  of  the  supply  water. 
With  other  patterns*  of  injector  in  which  the  priming  is 
effected  by  a  central  spindle  discharging  steam  through  the 
combining  or  delivery  tube,  such  as  the  Sellers'  1876  Injector, 


154  THE  GIFFARD  INJECTOR. 

the  Ohio,  Monitor  1888,  etc.,  repeat  the  same  method  of  proce- 
dure ;  examine  the  lifting  jet,  unscrewing  it  if  necessary,  to 
remove  any  obstructing  particle  of  coal  or  scale.  This  lift- 
ing jet  should  be  in  exact  line  with  the  other  tubes,  and  if 
bent,  discharges  the  steam  against  the  side  of  the  other 
nozzle  and  the  desired  vacuum  is  not  produced.  If  the  injec- 
tor is  of  the  double-jet  type,  the  Metropolitan,  Hancock, 
Schutte,  for  instance,  all  the  applicable  tests  above  described 
should  be  used ;  also,  ascertain  if  the  position  of  the  small 
spindle  which  regulates  the  steam  pressure  in  the  lifting  noz- 
zle permits  a  sufficient  amount  of  steam  to  enter,  and  then 
if  the  steam  valve  to  the  forcer  set  is  closed  when  the  lifter 
steam  valve  is  wide  open  ;  further,  there  may  be  interference 
with  the  free  discharge  of  the  steam  through  the  body,  owing 
to  inaccurate  setting  of  the  relief  or  overflow  valves  due  to 
wear  of  operating  parts  or  faulty  construction,  or  to  the  valves 
being  prevented  by  some  cause  from  lifting  from  their  seats  ; 
in  some  cases,  where  loose  valves  or  soft  seats  are  used,  they 
may  have  become  separated  from  their  attachments  and 
obstructed  some  of  the  waste  passages.  In  the  Improved 
Sellers',  1887,  and  the  1897  Monitor,  examine  the  inlet  valve 
in  the  passage  from  the  overflow  chamber  to  the  suction  ; 
this  valve  may  not  seat  firmly,  due  to  the  bending  of  the 
stem  or  to  some  obstruction  ;  this  valve  should  be  perfectly 
tight,  or  the  discharged  steam  from  the  lifting  nozzles  can 
pass  directly  into  the  suction  chamber. 

If  the  preliminary  test  showed  the  lifting  apparatus  to  be 
operative,  and  that  the  fault  lay  with  the  delivery  of  the 
feed  to  the  boiler,  the  methods  to  be  applied  would  depend 
upon  the  kind'  of  injector  and  its  action  when  steam  was 
admitted  to  the  forcing  nozzles.  If  the  injector  be  of  the 
simpler  type  a  heavy  waste  at  overflow  indicates  a  stoppage 
of  the  tubes,  or  that  the  delivery  tube  is  worn  too  large  for 
further  use ;  the  latter  condition  would  be  still  more  evident 
at  the  lower  pressures.  Another  possible  cause  of  trouble  is 
the  interference  with  the  jet  due  to  displacement,  breakage 
of  or  obstruction  by  the  line-check  valve.  In  some  forms 


FEEDING  LOCOMOTIVE  BOILERS.  155 

of  the  double-jet  type,  the  non  closing  of  the  overflow  relief 
valve  between  the  lifter  and  the  forcer  sets  prevents  the  pro- 
per inter-action  of  the  two  jets,  and  the  feed  water  will  not 
enter  the  boiler  ;  or,  the  tubes  of  the  lifter  or  forcer  may  be 
unequally  worn,  so  that  the  correct  ratios  are  lost,  and  either 
too  little  or  too  much  water  may  be  supplied  to  the  forcer 
tubes. 

The  injector  should  then  be  removed  from  the  locomotive, 
the  parts  carefully  unscrewed  and  examined  ;  if  the  diameters 
are  worn  too  much,  new  parts  should  be  subtituted  ;  exactly 
how  much  enlargement  is  permissible,  depends  upon  the 
kind  of  service  and  the  pattern  of  injector,  some  special 
styles  permitting  more  latitude  in  this  respect  than  others. 
One  of  the  best  practical  tests  of  the  superiority  of  an 
injector  is  the  length  of  service  without  removal  from  the 
engine,  and  the  cost  of  maintenance  ;  the  former  may  vary 
from  one  to  six  or  seven  years  ;  the  latter  depends  upon  the 
design,  the  cost  of  repair  parts,  and  the  condition  of  the 
water  and  steam  supplied  to  it.  It  is  often  possible  to  replace 
the  old  tubes  if  the  diameters  are  not  too  much  enlarged,  after 
the  interior  surfaces  have  been  carefully  smoothed  out  with 
fine  emery  cloth,  and  all  roughness  and  abrasion  removed, 
for  the  slightest  impediment  to  the  rapid  motion  of  the  moving 
mass  of  water  and  steam  interferes  with  the  action  of  the  jet. 

All  injectors  should  be  tested  before  replacing  upon  the 
boiler.  A  simple  form  of  testing  plant, — such  as  that  shown 
in  Fig.  43, — should  be  part  of  the  equipment  of  every 
large  railroad  shop  conducting  extensive  injector  repairs  ;  it 
should  be  connected  to  a  boiler  capable  of  carrying  as  high 
pressure  as  that  used  on  locomotives  ;  the  proving  test 
should  be  made  as  complete  as  possible,  and  a  permanent 
record  preserved  for  reference. 

FEEDING  LOCOMOTIVE  BOILERS. 

In  the  economical  handling  of  the  locomotive,  the  way  in 
which  the  boiler  is  fed  plays  an  important  part.  To  lay 
down  a  rigid  rule  is  manifestly  impossible,  but  that  generally 
accepted,  and  adopted  where  conditions  permit,  is  to  main- 


156  THE  GIFFARD  INJECTOR. 

tain  a  constant  water  level  with  a  continuous  feed.  There  are 
a  number  of  reasons  for  this  :  the  strains  on  the  boiler  sheets, 
due  to  changes  in  temperature  and  unequal  expansion,  are 
reduced  ;  the  drain  upon  the  steam  supply  is  more  constant, 
owing  to  the  continuous  operation  of  the  injector;  less 
water  is  wasted  in  stopping  and  starting  the  injector,  and 
less  time  and  attention  need  be  given  on  the  part  of  the 
operator;  on  long  level  runs,  this  method  can  almost 
always  be  pursued,  if  the  engineer  is  provided  with  an 
injector  having  a  wide  range  of  capacities  ;  but  there  are 
several  special  rules  to  be  observed  ;  in  approaching  a  sta- 
tion at  which  a  short  stop  is  made,  especially  between  long 
and  fast  runs,  it  is  advantageous  to  stop  the  injector  a  short 
time  before  the  station  is  reached,  to  permit  a  slight  checking 
of  the  fire,  and  then,  when  the  station  is  reached,  to  feed  the 
boilers  quickly  with  one,  or  even  with  both  injectors  if  neces- 
sary, to  prevent  blowing  off  at  the  safety-valve.  Also,  the 
feed  should  be  stopped  before  starting  from  a  station  ;  the 
train  can  then  be  drawn  out  with  full  boiler  pressure,  and 
there  need  be  no  drain  on  the  steam  supply  due  to  use  of 
the  injector,  until  the  train  is  under  good  headway  and  the 
exhaust  has  pulled  the  fire  into  good  working  condition. 
With  a  badly  steaming  or  overloaded  engine  drawing  a 
heavy  train  it  is  very  difficult  to  raise  the  pressure  to  the 
normal,  having  a  low  water  level  to  overcome  in  addition. 

A  curious  phenomenon,  often  observed  in  connection  with 
the  feeding  of  locomotive  boilers,  is  the  variation  in  the 
water  level  after  an  injector  has  been  started ;  when  a  boiler 
has  not  fed  for  some  time  and  the  engine  has  been  working 
hard  with  a  heavy  exhaust,  clear  fire  and  waste  gases  at  a 
high  temperature,  the  entire  body  of  water  is  filled  with 
bubbles  of  steam  working  upward  to  the  surface;  this 
mass  of  confined  air  and  steam  displaces  a  large  volume  of 
water,  while  the  agitation  of  the  surface  due  to  the  mo- 
tion of  the  engine  tends  still  further  to  raise  the  apparent 
water  level.  If  the  boiler  feeder  is  now  started,  the  cooler 
water  condenses  the  rising  steam  bubbles  and  diminishes  the 
volume  of  water,  and  lowers  the  level  in  the  glass.  In 


FEEDING  LOCOMOTIVE  BOILERS.  157 

former  days,  when  pumps  were  used,  five  to  ten  minutes 
were  often  required  before  any  increase  in  the  height  of  water 
would  be  shown,  and  although  the  injector  would  not  pro- 
duce so  marked  an  effect,  yet  a  deceptive  contraction  in  the 
volume  does  occur,  which  should  be  carefully  watched  ; 
otherwise,  when  normal  conditions  of  ebullition  are  estab- 
lished, it  will  be  found  that  the  water  level  has  risen  very 
suddenly,  at  the  probable  risk  of  water  passing  over  into 
the  cylinder. 

In  order  to  obtain  the  most  economical  results,  every 
device  used  on  and  about  a  locomotive  should  be  of  the  most 
efficient  pattern.  No  operator,  whether  on  a  railroad  or 
elsewhere,  can  do  his  best  for  his  employer  unless  he  is  sup- 
plied with  suitable  appliances  or  tools,  and  given  the  means 
whereby  he  can  be  most  economical  of  his  own  effort  and 
the  material  at  his  disposal.  This  is  especially  true  of  the 
injector,  which  should  be  arranged  to  give  good  results  with 
the  fewest  movements  and  with  the  least  inconvenience  to 
the  operator.  This  is  an  important  and  practical  question  : 
if  an  engineer  has  several  handles  to  manipulate  when  one 
should  answer  as  well,  or  if  fine  and  careful  adjustment  is 
required  to  give  good  results,  or  if  there  be  risk  of  breakage 
of  the  jet  when  throttling  to  the  minimum,  the  engineer 
will  operate  his  injector  as  best  suits  his  convenience, 
with  little  reference  to  the  finer  points  of  economy.  On  the 
other  hand,  all  good  men  are  ambitious  and  anxious  to  do 
their  best  and  make  records  for  themselves  which  may 
tend  to  their  advancement ;  if  an  engineer  or  fireman  feels 
that  he  can  obtain  good  results  and  will  receive  material 
encouragement  in  his  efforts,  he  will  steadily  improve.  Every- 
thing about  a  locomotive  should  be  the  best  of  its  kind, 
whether  air-brake,  lubricator  or  boiler-feeder,  and  should  be 
carefully  tested  by  the  motive-power  department,  and  full 
evidence  obtained  that  it  approaches  most  nearly  the  standard 
of  modern  excellence.  Great  advancement  has  already  been 
made,  yet  further  improvements  are  expected  at  the  hands 
of  those  who  are  working  toward  the  improvement  of  the 


158  THE  G1FFARD  INJECTOR. 

injector,  along  the  lines  laid  down  at  the  opening  of  this 
chapter. 

In  conclusion,  a  word  might  be  said  regarding  the  careful 
handling  of  injectors,  which  are  not  delicate  instruments, 
yet  require  occasional  attention  in  order  to  give  the  best 
satisfaction.  A  little  care  in  closing  the  valves  and  pushing 
in  levers  will  prolong  the  life  of  the  parts  and  reduce  the 
necessity  for  grinding  and  repairing.  If  dirt  or  scale  is 
caught  between  a  valve  and  its  seat,  causing  a  slight  leak,  a 
touch  with  a  seat  reamer  or  a  little  time  taken  to  grind  the 
surfaces  to  a  bearing,  will  save  much  future  trouble.  All 
valves  should  be  kept  tight,  as  a  leak  tends  invariably  to 
increase  rapidly,  and  the  trouble  is  magnified  if  repairs  are 
postponed.  The  deposit  of  a  hard  scale  upon  the  interior 
surfaces  of  the  tubes  and  in  the  overflow  vents  is  a  continual 
source  of  trouble  when  the  feed  water  contains  lime  in  solu- 
tion; a  small  amount  of  oil  fed  into  the  steam  or  suction 
pipes  alleviates  but  does  not  entirely  prevent  the  formation 
of  the  deposit ;  it  may,  however,  in  most  cases  be  removed 
by  allowing  the  tubes  to  remain  for  eight  or  ten  hours  in 
solution  of  one  part  of  muriatic  acid  in  ten  of  water. 

The  repairing  of  injectors  should  never  be  intrusted  to  a 
novice,  and  where  large  numbers  are  in  use,  it  is  customary 
on  large  railroads  to  combine  the  air  brake  and  injector 
repairs  in  the  same  department,  and  place  the  responsibility 
in  the  hands  of  experienced  workmen ;  every  opportunity 
should  be  afforded  these  men  for  obtaining  a  thorough 
knowledge  of  the  theory  of  action,  and  the  special  pecu- 
liarity of  each  pattern  of  injector  in  use,  and  it  has  been  the 
experience  of  the  author  that  courteous  attention  is  always 
given  by  the  well-known  manufacturing  companies  to  those 
who  seek  for  information. 


INDEX. 


AIR  IN  STEAM,  72. 

AUTOMATIC  DOUBLE  JET,  23. 

AUTOMATIC  INJECTOR — Definition  of, 
27  ;  Earliest  Forms  of,  22 ;  Exhaust, 
113;  Gresham,  no;  Manhattan, 
III;  Metropolitan,  109;  Penberthy, 
110-119;  Sellers'  1885,  108  ;  Sel- j 
lers'  1887,  104;  Webb,  92. 

BACK  PRESSURE,  119;  Effect  of  Feed- 
Temperature  Table,  72 ;  Experi- 
ments, 34,  122. 

BANCROFT,  J.  S. — Improvements  by,  22 

BELFIELD  INJECTOR,  66  ;  Description, 

102. 

BOURDON — Inventions  by,  3, 

BOILER  EVAPORATION,  126. 

BOILER  TESTERS,  121. 

BUFFALO  INJECTOR,  120. 

CAPACITY — See  Weight  of  Water  per 
Pound  of  Steam. 

COEFFICIENT  OF  IMPACT,  77,  78. 

COMBINING  TUBE,  45,  69;  Definition 
of,  26;  Losses  in,  74;  Vacuum 
Within,  49  ;  Wear  of,  51. 

DELIVERY  TEMPERATURE,  72,  78, 106. 

DELIVERY  TUBE — Definition  of,  26  ; 
Pressure  in,  33  ;  Wear  of,  42. 

DENSITY  OF  JET— Effect  of  Tempera- 
ture of  Feed,  78 ;  in  Delivery  Tube, 

31,  72. 

DESMOND— Improvements  by,  22. 
DIAGRAM — Maximum    and    Minimum 

Capacities  at  different  Feed  Temper- 


atures, 127;  Maximum  and  Mini- 
mum Capacities  at  different  Pres- 
sures, 125,  144;  Pressures  in  De- 
livery Tube,  40;  Pressure  within 
Steam  Nozzle,  57,  60;  Velocity  and 
Pressure  in  Delivery  Tube,  32. 

DIVERGENT  FLARE— Delivery  Tube, 
34,  39;  Steam  Nozzle,  54. 

DIVERGENT  STEAM  NOZZLE — Inven- 
tion of,  21. 

DOUBLE  JET — Automatic  Form  of,  23  ; 
Definition  of,  27 ;  Effect  of  Height 
of  Lift,  77;  Pressure  between  the 
two  sets  of  tubes,  78  ;  Relative  Pro- 
portions to  Single  Jet,  78. 

DOUBLE  JET  INJECTOR — Belfield,  102 ; 
Description  of,  19;  for  High  Feed 
Temperature,  50;  Schutte,  101. 

EBERMAN  INJECTOR,  114. 

EFFICIENCY— Cause  of  loss  of,  86; 
Compared  with  Pump,  87 ;  Defini- 
tion of,  28;  Mechanical,  84,  86;  of 
various  types,  66. 

EJECTORS,  123;  Definition  of,  25. 

ENGLISH  INJECTORS,  90. 

ENGLAND  —  Introduction  of  Injector 
into,  4. 

EXHAUST  INJECTOR,  64;  Description 
of,  118 ;  Length  of  Combining  Tube, 
48;  Theory  of  Action,  70. 

FEED  WATER — Purity  of,  51  ;  Tem- 
perature of,  50,  101,  106,  114, 
119,  147. 

159 


160 


INDEX. 


FEED  TEMPERATURE — Effect  upon  Ca- 
pacity, 78  ;  Effect  on  Maximum  and 
Minimum  Capacity  (Diagram),  133; 
Highest  Admissible  (Formula  for), 
85. 

FEEDING  LOCOMOTIVE  BOILERS,  155. 

FIRE  PUMPS,  123. 

FRANCE — Improvement  in,  20. 

FRENCH  INJECTORS,  93. 

FRIEDMAN — Improvements  by,  21. 

GARFIELD  INJECTOR,  32,  66,  109. 

GIFFARD,  H.  J.,  Original  inventor,  I. 

GIFFARD  INJECTOR,  10-32. 

GRESHAM  AND  CRAVEN,  92. 

GRESHAM,  JAMES — Improvements  by, 
18. 

GRESHAM  RE-STARTING  INJECTOR — 
Description  of,  116. 

HAMER,  METCALF  AND  DAVIES'  EX- 
HAUST INJECTOR,  21. 

HANCOCK  INJECTOR,  109. 

HANCOCK,  JOHN — Improvements  by, 
18. 

HOLDEN  AND  BROOKE — Improvements 
by,  23. 

HORSE  POWER  —  Required  to  Feed 
Boiler,  65. 

IMPACT— Coefficient  of  (Table),  72; 
Losses  during,  86. 

INJECTOR — Definition  of  Term,  25. 

IRWIN  INJECTOR,  48. 

ITALIAN  INJECTORS,  93. 

JENKS  INJECTOR,  120. 

KNEASS,  STRICKLAND  L. — Improve- 
ments by,  23. 

KORTING,  ERNEST — Improvements  by, 
1 8. 

LIFT — Effect  upon  Capacity  (Table), 
76. 

LITTLE  GIANT  INJECTOR  (RUE),  66; 
Description  of,  113;  Experiments 
with,  46. 

LOCOMOTIVE  INJECTORS  —  Sizes  Re- 
quired (Table),  121. 

LOFTUS,  JOHN — Improvements  by,  22. 

LOSSES  BY  CONDUCTION  OF  HEAT,  83. 


LOSSES  IN  COMBINING  TUBE,  69,  74. 

MACK  INJECTOR,  32,  66,  107. 

MANHATTAN  INJECTOR  —  Description 
of,  117. 

MAXIMUM   CAPACITY — Conditions   af- 
fecting, 119. 
I  MECHANICAL  EFFICIENCY,  64. 

METROPOLITAN  INJECTOR,  32,  66, 108, 

121. 

MILLHOLLAND — Improvements  by,  13. 
MINIMUM  CAPACITY — (Formula),  84. 
MONITOR  INJECTOR,  32,  36  ;    Descrip- 
|      tion  of,  97. 
MONITOR  STANDARD,  90. 
NATHAN  MFG.  Co.,  94. 
NON-LIFTING  INJECTOR,  89. 
OHIO  INJECTOR,  109. 
OIL — Use  of  to  Prevent  Scale,  129. 
PARK  INJECTOR,  120. 
PENBERTHY,  WILLIAM — Improvements 

by,  22. 
PENBERTHY  INJECTOR — Description  of, 

Il8;   "SPECIAL,"  IIO. 

PENNA.  R.  R.  STANDARD,  90,  129. 

PRESSURES  —  Within  Delivery  Tube 
(Diagram  of),  32;  Within  Steam 
Nozzle,  57. 

PUMP— Compared  with  Injector,  87. 

RANGE  OF  CAPACITY — Definition  of,  28. 

RE-STARTING — Sellers',  in. 

REPAIRS,  153. 

ROBINSON  AND  GRESHAM — Improve- 
ments by,  13. 

RUE  INJECTOR — See  "  LITTLE  GIANT." 

RUE,  SAMUEL — Improvements  by,  13. 

SCALE — Prevention  of,  158. 

ScHAU — Improvements  by,  21. 

SCHUTTE    (KORTING)     INJECTOR— De- 

scription  of,  100. 

SELF-ADJUSTING  INJECTOR — Action  of 
Combining  Tube,  48;  Advantages 
of,  47  ;  Definition  of,  27  ;  Descrip- 
tion of,  15,  96. 

SELLERS,  WM. — Inventor  of  Self-Ad- 
justing Principle,  14. 

SELLERS'  1876  INJECTOR,  32. 


INDEX. 


161 


SELLERS'  1885  INJECTOR — Description 
of,  ic8  ;  High  Feed  Temperature,  51. 

SELLERS'  RE-STARTING,  in. 

SELLERS'  1887  INJECTOR,  66;  De- 
scription of,  103. 

SETTING  INJECTORS,  120. 

STEAM  DISCHARGE,  58 ;  Phenomena 
of,  54;  Rate  of,  61,  63;  Formulae, 
61,  63. 

STEAM  JETS — Air  mixed  with,  71. 

STEAM  NOZZLE  —  Definition  of,  26 ; 
Ratios  Throat  to  Initial  Pressures, 
58,  60,  61. 

STEAM  PRESSURE — Effect  on  Maxi- 
mum and  Minimum  Capacity  (Dia 
gram),  124,  144. 

STEWART,  ROBINSON  AND  GRESHAM — 
Improvements  by,  20. 

TABLE  I. — Delivery  of  various  Injec- 
tors per  Unit  Area  of  Delivery  Tube, 

32. 
TABLE   II. — Pressure   and   Weight   of 

Water,  43. 

TABLE  III.— Values  of  0,  65. 
TABLE  IV  — Density  of  Jet  in  Delivery 

Tube,  72. 
TABLE  V. — Variation    of    Weight    of 

Water  per  Pound  of  Steam  with  Dif- 
ferent Heights  of  Lift,  76. 
TABLE   VI. —Tension    of    Vapor    of| 

Water,  77. 
TABLE    VII. — Variation    of    Capacity 

with  Feed  Temperature,  78. 


TABLE  VIII.— Weight  of  Water  per 
Pound  of  Steam  at  Different  Steam 
Pressures,  79. 

TESTS  OF  INJECTORS,  129. 

THEORY  OF  INJECTOR,  67. 

VABE— Early  Form  of  Automatic  In- 
jector, 22. 

VARIATION  OF  DENSITY  OF  JET  WITH 
FEED  TEMPERATURE  (Table),  72, 
78. 

VELOCITY  OF  STEAM  DISCHARGE,  55; 
At  various  pressures,  61  ;  Formulae, 
61  ;  At  Impact,  72. 

WATER — Weight  of  i  Cubic  Foot  of, 
at  various  Temperatures,  43. 

WATER  ENTRANCE  TO  COMBINING 
TUBE,  46. 

WATER  IN  STEAM,  64. 

WEAR — Combining  Tube,  51. 

WEBB'S  INJECTOR,  93. 

W.    F.    INJECTOR  —  Description    of, 

99- 

WEIGHT  OF  STEAM  DISCHARGE,  61 ; 
Experiments  and  Formulae,  63. 

WEIGHT  OF  WATER — Delivered  per 
Sq.  Mm.  of  Delivery  Tube,  66 ;  per 
Pound  of  Steam  (Formula  for),  76, 
83 ;  per  Pound  of  Steam  at  different 
Steam  Pressures,  79  ;  per  Pound  of 
Steam,  72,  146;  Variation  with  Feed 
Temperature,  78. 

WILLIAMS,  G.  C.— Automatic  Injector, 
22. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 


DEC    4  1947 


LD  21-100m-9,'47(A5702sl6)476 


YC   12874 


